| 10 | x | + | ( | 9 | − | x | ) | − | 27 | = | 10 | ( | 9 | − | x | ) | + | x |
| 方程左边 = | 10 | x | + | 9 | − | x | − | 27 |
| = | 9 | x | − | 18 |
| 9 | x | − | 18 | = | 10 | ( | 9 | − | x | ) | + | x |
| 方程右边 = | 10 | × | 9 | − | 10 | x | + | x |
| = | 90 | − | 10 | x | + | x |
| = | 90 | − | 9 | x |
| 9 | x | − | 18 | = | 90 | − | 9 | x |
| 9 | x | + | 9 | x | = | 90 | + | 18 |
| 18 | x | = | 90 | + | 18 |
| 18 | x | = | 108 |
| x | = | 108 | ÷ | 18 |
| = | 108 | × | 1 18 |
| = | 6 | × | 1 |
| x | = | 6 |