| ( | 80 | − | x | ) | × | 3 2 | = | ( | x | − | 25 | ) | × | 5 |
| 方程左边 = | 80 | × | 3 2 | − | x | × | 3 2 |
| = | 120 | − | x | × | 3 2 |
| 120 | − | 3 2 | x | = | ( | x | − | 25 | ) | × | 5 |
| 方程右边 = | x | × | 5 | − | 25 | × | 5 |
| = | x | × | 5 | − | 125 |
| 120 | − | 3 2 | x | = | 5 | x | − | 125 |
| - | 3 2 | x | − | 5 | x | = | - | 125 | − | 120 |
| - | 13 2 | x | = | - | 125 | − | 120 |
| - | 13 2 | x | = | - | 245 |
| 245 | = | 13 2 | x |
13 2 | x | = | 245 |
| x | = | 245 | ÷ | 13 2 |
| = | 245 | × | 2 13 |
| x | = | 490 13 |
| x | = | 37.692308 |