| 3 | ( | ( | - | ( | 4 | x | + | 4 | ) | + | 8 | ) | + | 12 | ) | − | 7 | = | 8 | x | − | 119 |
| 方程左边 = | 3 | ( | - | ( | 4 | x | + | 4 | ) | + | 8 | ) | + | 3 | × | 12 | − | 7 |
| = | 3 | ( | - | ( | 4 | x | + | 4 | ) | + | 8 | ) | + | 36 | − | 7 |
| = | 3 | ( | - | ( | 4 | x | + | 4 | ) | + | 8 | ) | + | 29 |
| = | - | 3 | ( | 4 | x | + | 4 | ) | + | 3 | × | 8 | + | 29 |
| = | - | 3 | ( | 4 | x | + | 4 | ) | + | 24 | + | 29 |
| = | - | 3 | ( | 4 | x | + | 4 | ) | + | 53 |
| = | - | 3 | × | 4 | x | − | 3 | × | 4 | + | 53 |
| = | - | 12 | x | − | 12 | + | 53 |
| = | - | 12 | x | + | 41 |
| - | 12 | x | + | 41 | = | 8 | x | − | 119 |
| - | 12 | x | − | 8 | x | = | - | 119 | − | 41 |
| - | 20 | x | = | - | 119 | − | 41 |
| - | 20 | x | = | - | 160 |
| 160 | = | 20 | x |
| 20 | x | = | 160 |
| x | = | 160 | ÷ | 20 |
| = | 160 | × | 1 20 |
| = | 8 | × | 1 |
| x | = | 8 |