| ( | 300 | − | x | ) | ÷ | ( | 80 | − | x | ) | = | 73 | ÷ | 23 |
| 方程两边同时乘以: | ( | 80 | − | x | ) |
| ( | 300 | − | x | ) | = | 73 | ÷ | 23 | × | ( | 80 | − | x | ) |
| 300 | − | x | = | 73 | ÷ | 23 | × | ( | 80 | − | x | ) |
| 300 | − | x | = | 73 | ÷ | 23 | × | 80 | − | 73 | ÷ | 23 | × | x |
| 300 | − | x | = | 5840 23 | − | 73 23 | x |
| - | x | + | 73 23 | x | = | 5840 23 | − | 300 |
50 23 | x | = | 5840 23 | − | 300 |
50 23 | x | = | - | 1060 23 |
| x | = | - | 1060 23 | ÷ | 50 23 |
| = | - | 1060 23 | × | 23 50 |
| = | - | 106 | × | 1 5 |
| x | = | - | 106 5 |
| x | = | - 21.2 |