| ( | 4000 | + | 100 | x | ) | x | − | 500 | x | − | ( | 100 | − | x | ) | × | 100 | = | 404000 |
| 方程左边 = | 4000 | x | + | 100 | x | x | − | 500 | x | − | ( | 100 | − | x | ) | × | 100 |
| = | 3500 | x | + | 100 | x | x | − | ( | 100 | − | x | ) | × | 100 |
| = | 3500 | x | + | 100 | x | x | − | 100 | × | 100 | + | x | × | 100 |
| = | 3500 | x | + | 100 | x | x | − | 10000 | + | x | × | 100 |
| = | 3600 | x | + | 100 | x | x | − | 10000 |
| 3600 | x | + | 100 | x | x | − | 10000 | = | 404000 |