| ( | 31 10 | − | x | ) | ( | 500 | x | + | 1950 | ) | = | 6000 |
| 方程左边 = | 31 10 | ( | 500 | x | + | 1950 | ) | − | x | ( | 500 | x | + | 1950 | ) |
| = | 31 10 | × | 500 | x | + | 31 10 | × | 1950 | − | x | ( | 500 | x | + | 1950 | ) |
| = | 1550 | x | + | 6045 | − | x | ( | 500 | x | + | 1950 | ) |
| = | 1550 | x | + | 6045 | − | x | × | 500 | x | − | x | × | 1950 |
| = | - | 400 | x | + | 6045 | − | x | × | 500 | x |
| - | 400 | x | + | 6045 | − | x | × | 500 | x | = | 6000 |
| x1= | - | 9 10 |
| x2= | 1 10 |