| 200 | ( | 1 | − | 5 100 | ) | × | 5 | ( | 1 | + | a% | ) | + | 400 | ( | 1 | − | 10 100 | ) | × | 5 | ( | 1 | + | a% | ) | × | 80 100 | = | 2102 |
| 方程左边 = | 1000 | ( | 1 | − | 5 100 | ) | ( | 1 | + | a% | ) | + | 1600 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| 1000 | ( | 1 | − | 5 100 | ) | ( | 1 | + | a% | ) | + | 1600 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) | = | 2102 |
| 方程左边 = | 1000 | × | 1 | ( | 1 | + | a% | ) | − | 1000 | × | 5 100 | ( | 1 | + | a% | ) | + | 1600 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 1000 | ( | 1 | + | a% | ) | − | 50 | ( | 1 | + | a% | ) | + | 1600 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 1000 | × | 1 | + | 1000 | × | a% | − | 50 | ( | 1 | + | a% | ) | + | 1600 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 1000 | + | 10 | a | − | 50 | ( | 1 | + | a% | ) | + | 1600 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 1000 | + | 10 | a | − | 50 | × | 1 | − | 50 | × | a% | + | 1600 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 1000 | + | 10 | a | − | 50 | − | 1 2 | a | + | 1600 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 950 | + | 19 2 | a | + | 1600 | ( | 1 | − | 10 100 | ) | ( | 1 | + | a% | ) |
| = | 950 | + | 19 2 | a | + | 1600 | × | 1 | ( | 1 | + | a% | ) | − | 1600 | × | 10 100 | ( | 1 | + | a% | ) |
| = | 950 | + | 19 2 | a | + | 1600 | ( | 1 | + | a% | ) | − | 160 | ( | 1 | + | a% | ) |
| = | 950 | + | 19 2 | a | + | 1600 | × | 1 | + | 1600 | × | a% | − | 160 | ( | 1 | + | a% | ) |
| = | 950 | + | 19 2 | a | + | 1600 | + | 16 | a | − | 160 | ( | 1 | + | a% | ) |
| = | 2550 | + | 51 2 | a | − | 160 | ( | 1 | + | a% | ) |
| = | 2550 | + | 51 2 | a | − | 160 | × | 1 | − | 160 | × | a% |
| = | 2550 | + | 51 2 | a | − | 160 | − | 8 5 | a |
| = | 2390 | + | 239 10 | a |
| 2390 | + | 239 10 | a | = | 2102 |
239 10 | a | = | 2102 | − | 2390 |
239 10 | a | = | - | 288 |
| a | = | - | 288 | ÷ | 239 10 |
| = | - | 288 | × | 10 239 |
| a | = | - | 2880 239 |
| a | = | - 12.050209 |