| 40 | ( | 1 | + | x% | ) | + | 50 | ( | 1 | − | 2 | × | x% | ) | = | 8320 |
| 方程左边 = | 40 | × | 1 | + | 40 | × | x% | + | 50 | ( | 1 | − | 2 | × | x% | ) |
| = | 40 | + | 2 5 | x | + | 50 | ( | 1 | − | 2 | × | x% | ) |
| = | 40 | + | 2 5 | x | + | 50 | × | 1 | − | 50 | × | 2 | × | x% |
| = | 40 | + | 2 5 | x | + | 50 | − | 1 | x |
| = | 90 | − | 3 5 | x |
| 90 | − | 3 5 | x | = | 8320 |
| - | 3 5 | x | = | 8320 | − | 90 |
| - | 3 5 | x | = | 8230 |
| - | 8230 | = | 3 5 | x |
3 5 | x | = | - | 8230 |
| x | = | - | 8230 | ÷ | 3 5 |
| = | - | 8230 | × | 5 3 |
| x | = | - | 41150 3 |
| x | = | - 13716.666667 |