| 27 | × | 21 | − | ( | 27 | − | 18 | x | ) | ( | 21 | − | 4 | x | ) | = | 119 |
| 方程左边 = | 567 | − | ( | 27 | − | 18 | x | ) | ( | 21 | − | 4 | x | ) |
| 567 | − | ( | 27 | − | 18 | x | ) | ( | 21 | − | 4 | x | ) | = | 119 |
| 方程左边 = | 567 | − | 27 | ( | 21 | − | 4 | x | ) | + | 18 | x | ( | 21 | − | 4 | x | ) |
| = | 567 | − | 27 | × | 21 | + | 27 | × | 4 | x | + | 18 | x | ( | 21 | − | 4 | x | ) |
| = | 567 | − | 567 | + | 108 | x | + | 18 | x | ( | 21 | − | 4 | x | ) |
| = | 0 | + | 108 | x | + | 18 | x | ( | 21 | − | 4 | x | ) |
| = | 108 | x | + | 18 | x | × | 21 | − | 18 | x | × | 4 | x |
| = | 108 | x | + | 378 | x | − | 72 | x | x |
| = | 486 | x | − | 72 | x | x |
| 486 | x | − | 72 | x | x | = | 119 |