| ( | 36 | − | 4 | x | ) | ( | 20 | − | 3 | x | ) | = | 36 | × | 20 | ( | 1 | − | 1 | ÷ | 5 | ) |
| 方程左边 = | 36 | ( | 20 | − | 3 | x | ) | − | 4 | x | ( | 20 | − | 3 | x | ) |
| = | 36 | × | 20 | − | 36 | × | 3 | x | − | 4 | x | ( | 20 | − | 3 | x | ) |
| = | 720 | − | 108 | x | − | 4 | x | ( | 20 | − | 3 | x | ) |
| = | 720 | − | 108 | x | − | 4 | x | × | 20 | + | 4 | x | × | 3 | x |
| = | 720 | − | 108 | x | − | 80 | x | + | 12 | x | x |
| = | 720 | − | 188 | x | + | 12 | x | x |
| 720 | − | 188 | x | + | 12 | x | x | = | 36 | × | 20 | ( | 1 | − | 1 | ÷ | 5 | ) |
| 方程右边 = | 720 | ( | 1 | − | 1 | ÷ | 5 | ) |
| 720 | − | 188 | x | + | 12 | x | x | = | 720 | ( | 1 | − | 1 | ÷ | 5 | ) |
| 方程右边 = | 720 | × | 1 | − | 720 | × | 1 | ÷ | 5 |
| = | 720 | − | 144 |
| = | 576 |
| 720 | − | 188 | x | + | 12 | x | x | = | 576 |