| ( | 150 | ( | 1 | − | 10 100 | ) | − | 100 | ) | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 40 | × | 20 | = | 2000 |
| 方程左边 = | ( | 150 | ( | 1 | − | 10 100 | ) | − | 100 | ) | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 800 |
| ( | 150 | ( | 1 | − | 10 100 | ) | − | 100 | ) | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 800 | = | 2000 |
| 方程左边 = | 150 | ( | 1 | − | 10 100 | ) | − | 100 | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 800 |
| = | 150 | × | 1 | − | 150 | × | 10 100 | − | 100 | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 800 |
| = | 150 | − | 15 | − | 100 | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 800 |
| = | 35 | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 800 |
| = | 35 | + | 225 | ( | 1 | − | a% | ) | × | 800 | − | 150 | × | 800 |
| = | 35 | + | 180000 | ( | 1 | − | a% | ) | − | 120000 |
| = | - | 119965 | + | 180000 | ( | 1 | − | a% | ) |
| = | - | 119965 | + | 180000 | × | 1 | − | 180000 | × | a% |
| = | - | 119965 | + | 180000 | − | 1800 | a |
| = | 60035 | − | 1800 | a |
| 60035 | − | 1800 | a | = | 2000 |
| - | 1800 | a | = | 2000 | − | 60035 |
| - | 1800 | a | = | - | 58035 |
| 58035 | = | 1800 | a |
| 1800 | a | = | 58035 |
| a | = | 58035 | ÷ | 1800 |
| = | 58035 | × | 1 1800 |
| = | 3869 | × | 1 120 |
| a | = | 3869 120 |
| a | = | 32.241667 |