| 31000 | = | X | − | ( | X | ÷ | ( | 1 | + | 3 100 | ) | × | 3 100 | ) | ( | 1 | + | 7 100 | ) | − | ( | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | − | 2000 | ) |
| 31000 | = | X | − | X | ÷ | ( | 1 | + | 3 100 | ) | × | 3 100 | ( | 1 | + | 7 100 | ) | − | ( | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | − | 2000 | ) |
| 方程两边同时乘以: | ( | 1 | + | 3 100 | ) |
| 31000 | ( | 1 | + | 3 100 | ) | = | X | ( | 1 | + | 3 100 | ) | − | X | × | 3 100 | ( | 1 | + | 7 100 | ) | − | ( | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | − | 2000 | ) | ( | 1 | + | 3 100 | ) |
| 31000 | × | 1 | + | 31000 | × | 3 100 | = | X | ( | 1 | + | 3 100 | ) | − | X | × | 3 100 | ( | 1 | + | 7 100 | ) | − | ( | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | − | 2000 | ) | ( | 1 | + | 3 100 | ) |
| 31000 | × | 1 | + | 31000 | × | 3 100 | = | X | × | 1 | + | X | × | 3 100 | − | X | × | 3 100 | ( | 1 | + | 7 100 | ) | − | ( | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | − | 2000 | ) | ( | 1 | + | 3 100 | ) |
| 31000 | + | 930 | = | X | × | 1 | + | X | × | 3 100 | − | X | × | 3 100 | ( | 1 | + | 7 100 | ) | − | ( | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | − | 2000 | ) | ( | 1 | + | 3 100 | ) |
| 31930 | = | 103 100 | X | − | X | × | 3 100 | ( | 1 | + | 7 100 | ) | − | ( | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | − | 2000 | ) | ( | 1 | + | 3 100 | ) |
| 31930 | = | 103 100 | X | − | X | × | 3 100 | × | 1 | − | X | × | 3 100 | × | 7 100 | − | ( | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | − | 2000 | ) | ( | 1 | + | 3 100 | ) |
| 31930 | = | 103 100 | X | − | X | × | 3 100 | − | X | × | 21 10000 | − | ( | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | − | 2000 | ) | ( | 1 | + | 3 100 | ) |
| 31930 | = | 9979 10000 | X | − | ( | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | − | 2000 | ) | ( | 1 | + | 3 100 | ) |
| 31930 | = | 9979 10000 | X | − | ( | X | ÷ | ( | 1 | + | 3 100 | ) | ) | ( | 1 | − | 20 100 | ) | × | 30 100 | ( | 1 | + | 3 100 | ) | + | 2000 | ( | 1 | + | 3 100 | ) |
| 31930 | = | 9979 10000 | X | − | X | ÷ | ( | 1 | + | 3 100 | ) | × | ( | 1 | − | 20 100 | ) | × | 30 100 | ( | 1 | + | 3 100 | ) | + | 2000 | ( | 1 | + | 3 100 | ) |
| 方程两边同时乘以: | ( | 1 | + | 3 100 | ) |
| 31930 | ( | 1 | + | 3 100 | ) | = | 9979 10000 | X | ( | 1 | + | 3 100 | ) | − | X | ( | 1 | − | 20 100 | ) | × | 30 100 | ( | 1 | + | 3 100 | ) | + | 2000 | ( | 1 | + | 3 100 | ) | ( | 1 | + | 3 100 | ) |
| 31930 | × | 1 | + | 31930 | × | 3 100 | = | 9979 10000 | X | ( | 1 | + | 3 100 | ) | − | X | ( | 1 | − | 20 100 | ) | × | 30 100 | ( | 1 | + | 3 100 | ) | + | 2000 | ( | 1 | + | 3 100 | ) | ( | 1 | + | 3 100 | ) |
| 31930 | × | 1 | + | 31930 | × | 3 100 | = | 9979 10000 | X | × | 1 | + | 9979 10000 | X | × | 3 100 | − | X | ( | 1 | − | 20 100 | ) | × | 30 100 | ( | 1 | + | 3 100 | ) | + | 2000 | ( | 1 | + | 3 100 | ) |
| 31930 | + | 9579 10 | = | 9979 10000 | X | + | 29937 1000000 | X | − | X | ( | 1 | − | 20 100 | ) | × | 30 100 | ( | 1 | + | 3 100 | ) | + | 2000 | ( | 1 | + | 3 100 | ) | ( | 1 | + | 3 100 | ) |