| - | 15 | ( | 8 | x | − | 7 | ) | + | 7 | ( | 18 | x | − | 1 | ) | − | 1 | = | - | 11 |
| 方程左边 = | - | 15 | × | 8 | x | + | 15 | × | 7 | + | 7 | ( | 18 | x | − | 1 | ) | − | 1 |
| = | - | 120 | x | + | 105 | + | 7 | ( | 18 | x | − | 1 | ) | − | 1 |
| = | - | 120 | x | + | 104 | + | 7 | ( | 18 | x | − | 1 | ) |
| = | - | 120 | x | + | 104 | + | 7 | × | 18 | x | − | 7 | × | 1 |
| = | - | 120 | x | + | 104 | + | 126 | x | − | 7 |
| = | 6 | x | + | 97 |
| 6 | x | + | 97 | = | - | 11 |
| 6 | x | = | - | 11 | − | 97 |
| 6 | x | = | - | 108 |
| x | = | - | 108 | ÷ | 6 |
| = | - | 108 | × | 1 6 |
| = | - | 18 | × | 1 |
| x | = | - | 18 |