| 200 | ( | 1 | − | 5 100 | ) | × | 5 | ( | 1 | + | a% | ) | + | 400 | ( | 1 | − | 10 100 | ) | × | 5 | × | 6 5 | ( | 1 | + | a% | ) | × | 80 100 | = | 2102 |
| 方程左边 = | 1000 | ( | 1 | − | 5 100 | ) | ( | 1 | + | a% | ) | + | 1920 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| 1000 | ( | 1 | − | 5 100 | ) | ( | 1 | + | a% | ) | + | 1920 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) | = | 2102 |
| 方程左边 = | 1000 | × | 1 | ( | 1 | + | a% | ) | − | 1000 | × | 5 100 | ( | 1 | + | a% | ) | + | 1920 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 1000 | ( | 1 | + | a% | ) | − | 50 | ( | 1 | + | a% | ) | + | 1920 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 1000 | × | 1 | + | 1000 | × | a% | − | 50 | ( | 1 | + | a% | ) | + | 1920 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 1000 | + | 10 | a | − | 50 | ( | 1 | + | a% | ) | + | 1920 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 1000 | + | 10 | a | − | 50 | × | 1 | − | 50 | × | a% | + | 1920 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 1000 | + | 10 | a | − | 50 | − | 1 2 | a | + | 1920 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 950 | + | 19 2 | a | + | 1920 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 950 | + | 19 2 | a | + | 1920 | × | 1 | ( | 1 | + | a% | ) | − | 1920 | × | 10 100 | ( | 1 | + | a% | ) |
| = | 950 | + | 19 2 | a | + | 1920 | ( | 1 | + | a% | ) | − | 192 | ( | 1 | + | a% | ) |
| = | 950 | + | 19 2 | a | + | 1920 | × | 1 | + | 1920 | × | a% | − | 192 | ( | 1 | + | a% | ) |
| = | 950 | + | 19 2 | a | + | 1920 | + | 96 5 | a | − | 192 | ( | 1 | + | a% | ) |
| = | 2870 | + | 287 10 | a | − | 192 | ( | 1 | + | a% | ) |
| = | 2870 | + | 287 10 | a | − | 192 | × | 1 | − | 192 | × | a% |
| = | 2870 | + | 287 10 | a | − | 192 | − | 48 25 | a |
| = | 2678 | + | 1339 50 | a |
| 2678 | + | 1339 50 | a | = | 2102 |
1339 50 | a | = | 2102 | − | 2678 |
1339 50 | a | = | - | 576 |
| a | = | - | 576 | ÷ | 1339 50 |
| = | - | 576 | × | 50 1339 |
| a | = | - | 28800 1339 |
| a | = | - 21.508588 |