| ( | 162 5 | + | x | ) | ( | 500 | − | 20 | x | ) | = | 0 |
| 方程左边 = | 162 5 | ( | 500 | − | 20 | x | ) | + | x | ( | 500 | − | 20 | x | ) |
| = | 162 5 | × | 500 | − | 162 5 | × | 20 | x | + | x | ( | 500 | − | 20 | x | ) |
| = | 16200 | − | 648 | x | + | x | ( | 500 | − | 20 | x | ) |
| = | 16200 | − | 648 | x | + | x | × | 500 | − | x | × | 20 | x |
| = | 16200 | − | 148 | x | − | x | × | 20 | x |
| 16200 | − | 148 | x | − | x | × | 20 | x | = | 0 |
| x1= | - | 162 5 |
| x2=25 |