| - | 6 | ( | x | + | 7 | ) | − | 9 | ( | x | − | 18 | ) | + | 1 | = | - | 14 |
| Left side of the equation = | - | 6 | x | − | 6 | × | 7 | − | 9 | ( | x | − | 18 | ) | + | 1 |
| = | - | 6 | x | − | 42 | − | 9 | ( | x | − | 18 | ) | + | 1 |
| = | - | 6 | x | − | 41 | − | 9 | ( | x | − | 18 | ) |
| = | - | 6 | x | − | 41 | − | 9 | x | + | 9 | × | 18 |
| = | - | 6 | x | − | 41 | − | 9 | x | + | 162 |
| = | - | 15 | x | + | 121 |
| - | 15 | x | + | 121 | = | - | 14 |
| - | 15 | x | = | - | 14 | − | 121 |
| - | 15 | x | = | - | 135 |
| 135 | = | 15 | x |
| 15 | x | = | 135 |
| x | = | 135 | ÷ | 15 |
| = | 135 | × | 1 15 |
| = | 9 | × | 1 |
| x | = | 9 |