| 120 | ( | 1 | + | 2 | × | a% | ) | × | 9 10 | + | 80 | ( | 1 | + | a% | ) | − | 120 | × | 200 | − | 80 | × | 150 | = | 14160 |
| 方程左边 = | 108 | ( | 1 | + | 2 | × | a% | ) | + | 80 | ( | 1 | + | a% | ) | − | 24000 | − | 12000 |
| = | 108 | ( | 1 | + | 2 | × | a% | ) | + | 80 | ( | 1 | + | a% | ) | − | 36000 |
| 108 | ( | 1 | + | 2 | × | a% | ) | + | 80 | ( | 1 | + | a% | ) | − | 36000 | = | 14160 |
| 方程左边 = | 108 | × | 1 | + | 108 | × | 2 | × | a% | + | 80 | ( | 1 | + | a% | ) | − | 36000 |
| = | 108 | + | 54 25 | a | + | 80 | ( | 1 | + | a% | ) | − | 36000 |
| = | - | 35892 | + | 54 25 | a | + | 80 | ( | 1 | + | a% | ) |
| = | - | 35892 | + | 54 25 | a | + | 80 | × | 1 | + | 80 | × | a% |
| = | - | 35892 | + | 54 25 | a | + | 80 | + | 4 5 | a |
| = | - | 35812 | + | 74 25 | a |
| - | 35812 | + | 74 25 | a | = | 14160 |
74 25 | a | = | 14160 | + | 35812 |
74 25 | a | = | 49972 |
| a | = | 49972 | ÷ | 74 25 |
| = | 49972 | × | 25 74 |
| = | 24986 | × | 25 37 |
| a | = | 624650 37 |
| a | = | 16882.432432 |