| 90 | × | 600 | ( | 1 | − | a% | ) | + | 120 | × | 180 | ( | 1 | − | 9 | ÷ | 5 | × | a% | ) | = | 62400 |
| 方程左边 = | 54000 | ( | 1 | − | a% | ) | + | 21600 | ( | 1 | − | 9 | ÷ | 5 | × | a% | ) |
| 54000 | ( | 1 | − | a% | ) | + | 21600 | ( | 1 | − | 9 | ÷ | 5 | × | a% | ) | = | 62400 |
| 方程左边 = | 54000 | × | 1 | − | 54000 | × | a% | + | 21600 | ( | 1 | − | 9 | ÷ | 5 | × | a% | ) |
| = | 54000 | − | 540 | a | + | 21600 | ( | 1 | − | 9 | ÷ | 5 | × | a% | ) |
| = | 54000 | − | 540 | a | + | 21600 | × | 1 | − | 21600 | × | 9 | ÷ | 5 | × | a% |
| = | 54000 | − | 540 | a | + | 21600 | − | 1944 5 | a |
| = | 75600 | − | 4644 5 | a |
| 75600 | − | 4644 5 | a | = | 62400 |
| - | 4644 5 | a | = | 62400 | − | 75600 |
| - | 4644 5 | a | = | - | 13200 |
| 13200 | = | 4644 5 | a |
4644 5 | a | = | 13200 |
| a | = | 13200 | ÷ | 4644 5 |
| = | 13200 | × | 5 4644 |
| = | 1100 | × | 5 387 |
| a | = | 5500 387 |
| a | = | 14.211886 |