| - | 6 | + | 5 | ( | 7 | + | 2 | ( | 15 | + | x | ) | ) | = | 9 | ( | 12 | x | + | 9 | ) |
| 方程左边 = | - | 6 | + | 5 | × | 7 | + | 5 | × | 2 | ( | 15 | + | x | ) |
| = | - | 6 | + | 35 | + | 10 | ( | 15 | + | x | ) |
| = | 29 | + | 10 | ( | 15 | + | x | ) |
| = | 29 | + | 10 | × | 15 | + | 10 | x |
| = | 29 | + | 150 | + | 10 | x |
| = | 179 | + | 10 | x |
| 179 | + | 10 | x | = | 9 | ( | 12 | x | + | 9 | ) |
| 方程右边 = | 9 | × | 12 | x | + | 9 | × | 9 |
| = | 108 | x | + | 81 |
| 179 | + | 10 | x | = | 108 | x | + | 81 |
| 10 | x | − | 108 | x | = | 81 | − | 179 |
| - | 98 | x | = | 81 | − | 179 |
| - | 98 | x | = | - | 98 |
| 98 | = | 98 | x |
| 98 | x | = | 98 |
| x | = | 98 | ÷ | 98 |
| = | 98 | × | 1 98 |
| = | 1 | × | 1 |
| x | = | 1 |