| 7 | ( | x | − | 4 | ) | − | 7 | ( | 7 | − | x | ) | − | 9 | = | 12 | − | 3 | ( | 9 | − | x | ) |
| 方程左边 = | 7 | x | − | 7 | × | 4 | − | 7 | ( | 7 | − | x | ) | − | 9 |
| = | 7 | x | − | 28 | − | 7 | ( | 7 | − | x | ) | − | 9 |
| = | 7 | x | − | 37 | − | 7 | ( | 7 | − | x | ) |
| = | 7 | x | − | 37 | − | 7 | × | 7 | + | 7 | x |
| = | 7 | x | − | 37 | − | 49 | + | 7 | x |
| = | 14 | x | − | 86 |
| 14 | x | − | 86 | = | 12 | − | 3 | ( | 9 | − | x | ) |
| 方程右边 = | 12 | − | 3 | × | 9 | + | 3 | x |
| = | 12 | − | 27 | + | 3 | x |
| = | - | 15 | + | 3 | x |
| 14 | x | − | 86 | = | - | 15 | + | 3 | x |
| 14 | x | − | 3 | x | = | - | 15 | + | 86 |
| 11 | x | = | - | 15 | + | 86 |
| 11 | x | = | 71 |
| x | = | 71 | ÷ | 11 |
| = | 71 | × | 1 11 |
| x | = | 71 11 |
| x | = | 6.454545 |