| ( | y | − | 2500 | ) | ( | ( | 2900 | − | y | ) | ÷ | 50 | ) | = | 5000 |
| 方程左边 = | y | ( | ( | 2900 | − | y | ) | ÷ | 50 | ) | − | 2500 | ( | ( | 2900 | − | y | ) | ÷ | 50 | ) |
| = | y | ( | 2900 | − | y | ) | ÷ | 50 | − | 2500 | ( | ( | 2900 | − | y | ) | ÷ | 50 | ) |
| = | y | × | 2900 | × | 1 50 | − | y | y | × | 1 50 | − | 2500 | ( | ( | 2900 | − | y | ) | ÷ | 50 | ) |
| = | y | × | 58 | − | y | y | × | 1 50 | − | 2500 | ( | ( | 2900 | − | y | ) | ÷ | 50 | ) |
| = | 58 | y | − | y | y | × | 1 50 | − | 2500 | ( | 2900 | − | y | ) | ÷ | 50 |
| = | 58 | y | − | y | y | × | 1 50 | − | 50 | ( | 2900 | − | y | ) |
| = | 58 | y | − | y | y | × | 1 50 | − | 50 | × | 2900 | + | 50 | y |
| = | 58 | y | − | y | y | × | 1 50 | − | 145000 | + | 50 | y |
| = | 108 | y | − | y | y | × | 1 50 | − | 145000 |
| 108 | y | − | y | y | × | 1 50 | − | 145000 | = | 5000 |