| - | 2 | ( | ( | ( | x | + | 10 | ) | − | 2 | ) | + | 7 | ) | + | 2 | = | 3 | x | + | 42 |
| 方程左边 = | - | 2 | ( | ( | x | + | 10 | ) | − | 2 | ) | − | 2 | × | 7 | + | 2 |
| = | - | 2 | ( | ( | x | + | 10 | ) | − | 2 | ) | − | 14 | + | 2 |
| = | - | 2 | ( | ( | x | + | 10 | ) | − | 2 | ) | − | 12 |
| = | - | 2 | ( | x | + | 10 | ) | + | 2 | × | 2 | − | 12 |
| = | - | 2 | ( | x | + | 10 | ) | + | 4 | − | 12 |
| = | - | 2 | ( | x | + | 10 | ) | − | 8 |
| = | - | 2 | x | − | 2 | × | 10 | − | 8 |
| = | - | 2 | x | − | 20 | − | 8 |
| = | - | 2 | x | − | 28 |
| - | 2 | x | − | 28 | = | 3 | x | + | 42 |
| - | 2 | x | − | 3 | x | = | 42 | + | 28 |
| - | 5 | x | = | 42 | + | 28 |
| - | 5 | x | = | 70 |
| - | 70 | = | 5 | x |
| 5 | x | = | - | 70 |
| x | = | - | 70 | ÷ | 5 |
| = | - | 70 | × | 1 5 |
| = | - | 14 | × | 1 |
| x | = | - | 14 |