| 7250000 | = | 7200 | ( | 1000 | − | 1200 | b | ) |
| 方程右边 = | 7200 | × | 1000 | − | 7200 | × | 1200 | b |
| = | 7200000 | − | 8640000 | b |
| 7250000 | = | 7200000 | − | 8640000 | b |
| 8640000 | b | = | 7200000 | − | 7250000 |
| 8640000 | b | = | - | 50000 |
| b | = | - | 50000 | ÷ | 8640000 |
| = | - | 50000 | × | 1 8640000 |
| = | - | 5 | × | 1 864 |
| b | = | - | 5 864 |
| b | = | - 0.005787 |