| 55 | ( | x | − | 1 | ) | = | 50 | ( | x | − | 2 | ) | + | 170 |
| 方程左边 = | 55 | x | − | 55 | × | 1 |
| = | 55 | x | − | 55 |
| 55 | x | − | 55 | = | 50 | ( | x | − | 2 | ) | + | 170 |
| 方程右边 = | 50 | x | − | 50 | × | 2 | + | 170 |
| = | 50 | x | − | 100 | + | 170 |
| = | 50 | x | + | 70 |
| 55 | x | − | 55 | = | 50 | x | + | 70 |
| 55 | x | − | 50 | x | = | 70 | + | 55 |
| 5 | x | = | 70 | + | 55 |
| 5 | x | = | 125 |
| x | = | 125 | ÷ | 5 |
| = | 125 | × | 1 5 |
| = | 25 | × | 1 |
| x | = | 25 |