| ( | 15 100 | − | ( | 100 100 | − | 80 100 | − | X | ) | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | = | 75000 | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 25000 | ÷ | 80 100 | ) |
15 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | = | 75000 | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 25000 | ÷ | 80 100 | ) |
15 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | = | 75000 | − | 100 100 | ( | 25000 | ÷ | 80 100 | ) | + | 80 100 | ( | 25000 | ÷ | 80 100 | ) | + | X | ( | 25000 | ÷ | 80 100 | ) |
15 100 | × | 60000 | − | 15 100 | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | = | 75000 | − | 100 100 | ( | 25000 | ÷ | 80 100 | ) | + | 80 100 | ( | 25000 | ÷ | 80 100 | ) | + | X | ( | 25000 | ÷ | 80 100 | ) |
15 100 | × | 60000 | − | 15 100 | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | = | 75000 | − | 100 100 | × | 25000 | ÷ | 80 100 | + | 80 100 | ( | 25000 | ÷ | 80 100 | ) | + | X | ( | 25000 | ÷ | 80 100 | ) |
| 9000 | − | 15 100 | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | = | 75000 | − | 31250 | + | 80 100 | ( | 25000 | ÷ | 80 100 | ) | + | X | ( | 25000 | ÷ | 80 100 | ) |
| 9000 | − | 15 100 | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | = | 43750 | + | 80 100 | ( | 25000 | ÷ | 80 100 | ) | + | X | ( | 25000 | ÷ | 80 100 | ) |
| 方程两边同时乘以: | ( | 18 100 | − | X | ) |
| 9000 | ( | 18 100 | − | X | ) | − | 15 100 | X | ( | 25000 | ÷ | 80 100 | ) | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 43750 | ( | 18 100 | − | X | ) | + | 80 100 | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 9000 | × | 18 100 | − | 9000 | X | − | 15 100 | X | ( | 25000 | ÷ | 80 100 | ) | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 43750 | ( | 18 100 | − | X | ) | + | 80 100 | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 9000 | × | 18 100 | − | 9000 | X | − | 15 100 | X | ( | 25000 | ÷ | 80 100 | ) | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 43750 | × | 18 100 | − | 43750 | X | + | 80 100 | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 9000 | X | − | 15 100 | X | ( | 25000 | ÷ | 80 100 | ) | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 7875 | − | 43750 | X | + | 80 100 | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 9000 | X | − | 15 100 | X | × | 25000 | ÷ | 80 100 | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 7875 | − | 43750 | X | + | 80 100 | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 9000 | X | − | 15 100 | X | × | 25000 | ÷ | 80 100 | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 7875 | − | 43750 | X | + | 80 100 | × | 25000 | ÷ | 80 100 | × | ( | 18 100 | − | X | ) | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 9000 | X | − | 9375 2 | X | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 7875 | − | 43750 | X | + | 25000 | ( | 18 100 | − | X | ) | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 27375 2 | X | − | ( | 100 100 | − | 80 100 | − | X | ) | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 7875 | − | 43750 | X | + | 25000 | ( | 18 100 | − | X | ) | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 27375 2 | X | − | 100 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | + | 80 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | + | X | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 7875 | − | 43750 | X | + | 25000 | ( | 18 100 | − | X | ) | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 27375 2 | X | − | 100 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | + | 80 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | + | X | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 7875 | − | 43750 | X | + | 25000 | × | 18 100 | − | 25000 | X | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 27375 2 | X | − | 100 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | + | 80 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | + | X | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 7875 | − | 43750 | X | + | 4500 | − | 25000 | X | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 27375 2 | X | − | 100 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | + | 80 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | + | X | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | ( | 18 100 | − | X | ) | = | 12375 | − | 68750 | X | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 27375 2 | X | − | 100 100 | × | 60000 | ( | 18 100 | − | X | ) | + | 100 100 | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | × | ( | 18 100 | − | X | ) | + | 80 100 | = | 12375 | − | 68750 | X | + | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) |
| 1620 | − | 27375 2 | X | − | 100 100 | × | 60000 | ( | 18 100 | − | X | ) | + | 100 100 | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | × | ( | 18 100 | − | X | ) | + | 80 100 | = | 12375 | − | 68750 | X | + | X | × | 25000 | ÷ | 80 100 | × | ( | 18 100 | − | X | ) |
| 1620 | − | 27375 2 | X | − | 60000 | ( | 18 100 | − | X | ) | + | 100 100 | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | × | ( | 18 100 | − | X | ) | + | 80 100 | ( | 60000 | − | X | ( | 25000 | ÷ | 80 100 | ) | ÷ | ( | 18 100 | − | X | ) | ) | = | 12375 | − | 68750 | X | + | X | × | 31250 | ( | 18 100 | − | X | ) |
| 方程两边同时乘以: | ( | 18 100 | − | X | ) |
| 1620 | ( | 18 100 | − | X | ) | − | 27375 2 | X | ( | 18 100 | − | X | ) | − | 60000 | ( | 18 100 | − | X | ) | ( | 18 100 | − | X | ) | + | 100 100 | X | ( | 25000 | ÷ | 80 100 | ) | ( | 18 100 | − | X | ) | = | 12375 | ( | 18 100 | − | X | ) | − | 68750 | X | ( | 18 100 | − | X | ) | + | X | × | 31250 | ( | 18 100 | − | X | ) | ( | 18 100 | − | X | ) |
| 1620 | × | 18 100 | − | 1620 | X | − | 27375 2 | X | ( | 18 100 | − | X | ) | − | 60000 | ( | 18 100 | − | X | ) | ( | 18 100 | − | X | ) | + | 100 100 | X | = | 12375 | ( | 18 100 | − | X | ) | − | 68750 | X | ( | 18 100 | − | X | ) | + | X | × | 31250 | ( | 18 100 | − | X | ) | ( | 18 100 | − | X | ) |