| 12 | − | 2 | ( | 2 | x | + | 1 | ) | = | 3 | ( | 1 | + | x | ) |
| 方程左边 = | 12 | − | 2 | × | 2 | x | − | 2 | × | 1 |
| = | 12 | − | 4 | x | − | 2 |
| = | 10 | − | 4 | x |
| 10 | − | 4 | x | = | 3 | ( | 1 | + | x | ) |
| 方程右边 = | 3 | × | 1 | + | 3 | x |
| = | 3 | + | 3 | x |
| 10 | − | 4 | x | = | 3 | + | 3 | x |
| - | 4 | x | − | 3 | x | = | 3 | − | 10 |
| - | 7 | x | = | 3 | − | 10 |
| - | 7 | x | = | - | 7 |
| 7 | = | 7 | x |
| 7 | x | = | 7 |
| x | = | 7 | ÷ | 7 |
| = | 7 | × | 1 7 |
| = | 1 | × | 1 |
| x | = | 1 |