| 50 | ( | x | + | 6 | ) | = | 60 | ( | x | − | 7 | ) |
| 方程左边 = | 50 | x | + | 50 | × | 6 |
| = | 50 | x | + | 300 |
| 50 | x | + | 300 | = | 60 | ( | x | − | 7 | ) |
| 方程右边 = | 60 | x | − | 60 | × | 7 |
| = | 60 | x | − | 420 |
| 50 | x | + | 300 | = | 60 | x | − | 420 |
| 50 | x | − | 60 | x | = | - | 420 | − | 300 |
| - | 10 | x | = | - | 420 | − | 300 |
| - | 10 | x | = | - | 720 |
| 720 | = | 10 | x |
| 10 | x | = | 720 |
| x | = | 720 | ÷ | 10 |
| = | 720 | × | 1 10 |
| = | 72 | × | 1 |
| x | = | 72 |