| 100 | ( | 95 | − | x | ) | − | 80 | ( | 100 | − | x | ) | = | 100 |
| 方程左边 = | 100 | × | 95 | − | 100 | x | − | 80 | ( | 100 | − | x | ) |
| = | 9500 | − | 100 | x | − | 80 | ( | 100 | − | x | ) |
| = | 9500 | − | 100 | x | − | 80 | × | 100 | + | 80 | x |
| = | 9500 | − | 100 | x | − | 8000 | + | 80 | x |
| = | 1500 | − | 20 | x |
| 1500 | − | 20 | x | = | 100 |
| - | 20 | x | = | 100 | − | 1500 |
| - | 20 | x | = | - | 1400 |
| 1400 | = | 20 | x |
| 20 | x | = | 1400 |
| x | = | 1400 | ÷ | 20 |
| = | 1400 | × | 1 20 |
| = | 70 | × | 1 |
| x | = | 70 |