| ( | 150 | ( | 1 | − | 1 10 | ) | − | 100 | ) | × | 20 | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 10 | = | 1000 |
| 方程左边 = | 150 | ( | 1 | − | 1 10 | ) | × | 20 | − | 100 | × | 20 | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 10 |
| = | 3000 | ( | 1 | − | 1 10 | ) | − | 2000 | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 10 |
| = | 3000 | × | 1 | − | 3000 | × | 1 10 | − | 2000 | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 10 |
| = | 3000 | − | 300 | − | 2000 | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 10 |
| = | 700 | + | ( | 225 | ( | 1 | − | a% | ) | − | 150 | ) | × | 10 |
| = | 700 | + | 225 | ( | 1 | − | a% | ) | × | 10 | − | 150 | × | 10 |
| = | 700 | + | 2250 | ( | 1 | − | a% | ) | − | 1500 |
| = | - | 800 | + | 2250 | ( | 1 | − | a% | ) |
| = | - | 800 | + | 2250 | × | 1 | − | 2250 | × | a% |
| = | - | 800 | + | 2250 | − | 45 2 | a |
| = | 1450 | − | 45 2 | a |
| 1450 | − | 45 2 | a | = | 1000 |
| - | 45 2 | a | = | 1000 | − | 1450 |
| - | 45 2 | a | = | - | 450 |
| 450 | = | 45 2 | a |
45 2 | a | = | 450 |
| a | = | 450 | ÷ | 45 2 |
| = | 450 | × | 2 45 |
| = | 10 | × | 2 |
| a | = | 20 |