| 7 | ( | 2 | x | − | 1 | ) | − | 3 | ( | 3 | x | + | 5 | ) | + | 1 | = | 2 | ( | 9 | x | − | 4 | ) |
| 方程左边 = | 7 | × | 2 | x | − | 7 | × | 1 | − | 3 | ( | 3 | x | + | 5 | ) | + | 1 |
| = | 14 | x | − | 7 | − | 3 | ( | 3 | x | + | 5 | ) | + | 1 |
| = | 14 | x | − | 6 | − | 3 | ( | 3 | x | + | 5 | ) |
| = | 14 | x | − | 6 | − | 3 | × | 3 | x | − | 3 | × | 5 |
| = | 14 | x | − | 6 | − | 9 | x | − | 15 |
| = | 5 | x | − | 21 |
| 5 | x | − | 21 | = | 2 | ( | 9 | x | − | 4 | ) |
| 方程右边 = | 2 | × | 9 | x | − | 2 | × | 4 |
| = | 18 | x | − | 8 |
| 5 | x | − | 21 | = | 18 | x | − | 8 |
| 5 | x | − | 18 | x | = | - | 8 | + | 21 |
| - | 13 | x | = | - | 8 | + | 21 |
| - | 13 | x | = | 13 |
| - | 13 | = | 13 | x |
| 13 | x | = | - | 13 |
| x | = | - | 13 | ÷ | 13 |
| = | - | 13 | × | 1 13 |
| = | - | 1 | × | 1 |
| x | = | - | 1 |