| 3 | x | − | 2 | ( | 15 | + | x | ) | = | 5 | x | − | 3 | ( | 17 | − | x | ) |
| 方程左边 = | 3 | x | − | 2 | × | 15 | − | 2 | x |
| = | 3 | x | − | 30 | − | 2 | x |
| = | 1 | x | − | 30 |
| 1 | x | − | 30 | = | 5 | x | − | 3 | ( | 17 | − | x | ) |
| 方程右边 = | 5 | x | − | 3 | × | 17 | + | 3 | x |
| = | 5 | x | − | 51 | + | 3 | x |
| = | 8 | x | − | 51 |
| 1 | x | − | 30 | = | 8 | x | − | 51 |
| 1 | x | − | 8 | x | = | - | 51 | + | 30 |
| - | 7 | x | = | - | 51 | + | 30 |
| - | 7 | x | = | - | 21 |
| 21 | = | 7 | x |
| 7 | x | = | 21 |
| x | = | 21 | ÷ | 7 |
| = | 21 | × | 1 7 |
| = | 3 | × | 1 |
| x | = | 3 |