| ( | 10 | x | + | ( | 7 | − | x | ) | ) | − | ( | 10 | ( | 7 | − | x | ) | + | x | ) | = | 27 |
| 方程左边 = | 10 | x | + | ( | 7 | − | x | ) | − | ( | 10 | ( | 7 | − | x | ) | + | x | ) |
| = | 10 | x | + | 7 | − | x | − | ( | 10 | ( | 7 | − | x | ) | + | x | ) |
| = | 9 | x | + | 7 | − | ( | 10 | ( | 7 | − | x | ) | + | x | ) |
| = | 9 | x | + | 7 | − | 10 | ( | 7 | − | x | ) | − | x |
| = | 8 | x | + | 7 | − | 10 | ( | 7 | − | x | ) |
| = | 8 | x | + | 7 | − | 10 | × | 7 | + | 10 | x |
| = | 8 | x | + | 7 | − | 70 | + | 10 | x |
| = | 18 | x | − | 63 |
| 18 | x | − | 63 | = | 27 |
| 18 | x | = | 27 | + | 63 |
| 18 | x | = | 90 |
| x | = | 90 | ÷ | 18 |
| = | 90 | × | 1 18 |
| = | 5 | × | 1 |
| x | = | 5 |