| 100 | ( | 1 | − | m% | ) | × | 30 | + | 200 | ( | 1 | + | 2 | × | m% | ) | ( | 30 | ( | 1 | − | m% | ) | ) | = | 7000 |
| 方程左边 = | 3000 | ( | 1 | − | m% | ) | + | 200 | ( | 1 | + | 2 | × | m% | ) | ( | 30 | ( | 1 | − | m% | ) | ) |
| 3000 | ( | 1 | − | m% | ) | + | 200 | ( | 1 | + | 2 | × | m% | ) | ( | 30 | ( | 1 | − | m% | ) | ) | = | 7000 |
| 方程左边 = | 3000 | × | 1 | − | 3000 | × | m% | + | 200 | ( | 1 | + | 2 | × | m% | ) | ( | 30 | ( | 1 | − | m% | ) | ) |
| = | 3000 | − | 30 | m | + | 200 | ( | 1 | + | 2 | × | m% | ) | ( | 30 | ( | 1 | − | m% | ) | ) |
| = | 3000 | − | 30 | m | + | 200 | × | 1 | ( | 30 | ( | 1 | − | m% | ) | ) | + | 200 | × | 2 | × | m% | ( | 30 | ( | 1 | − | m% | ) | ) |
| = | 3000 | − | 30 | m | + | 200 | ( | 30 | ( | 1 | − | m% | ) | ) | + | 4 | m | ( | 30 | ( | 1 | − | m% | ) | ) |
| = | 3000 | − | 30 | m | + | 200 | × | 30 | ( | 1 | − | m% | ) | + | 4 | m | ( | 30 | ( | 1 | − | m% | ) | ) |
| = | 3000 | − | 30 | m | + | 6000 | ( | 1 | − | m% | ) | + | 4 | m | ( | 30 | ( | 1 | − | m% | ) | ) |
| = | 3000 | − | 30 | m | + | 6000 | × | 1 | − | 6000 | × | m% | + | 4 | m | ( | 30 | ( | 1 | − | m% | ) | ) |
| = | 3000 | − | 30 | m | + | 6000 | − | 60 | m | + | 4 | m | ( | 30 | ( | 1 | − | m% | ) | ) |
| = | 9000 | − | 90 | m | + | 4 | m | ( | 30 | ( | 1 | − | m% | ) | ) |
| = | 9000 | − | 90 | m | + | 4 | m | × | 30 | ( | 1 | − | m% | ) |
| = | 9000 | − | 90 | m | + | 120 | m | ( | 1 | − | m% | ) |
| = | 9000 | − | 90 | m | + | 120 | m | × | 1 | − | 120 | m | × | m% |
| = | 9000 | − | 90 | m | + | 120 | m | − | 6 5 | m | m |
| = | 9000 | + | 30 | m | − | 6 5 | m | m |
| 9000 | + | 30 | m | − | 6 5 | m | m | = | 7000 |