| ( | 500 | − | x | ) | ( | 10 | + | 1 20 | x | ) | = | 6000 |
| 方程左边 = | 500 | ( | 10 | + | 1 20 | x | ) | − | x | ( | 10 | + | 1 20 | x | ) |
| = | 500 | × | 10 | + | 500 | × | 1 20 | x | − | x | ( | 10 | + | 1 20 | x | ) |
| = | 5000 | + | 25 | x | − | x | ( | 10 | + | 1 20 | x | ) |
| = | 5000 | + | 25 | x | − | x | × | 10 | − | x | × | 1 20 | x |
| = | 5000 | + | 15 | x | − | x | × | 1 20 | x |
| 5000 | + | 15 | x | − | x | × | 1 20 | x | = | 6000 |