| 1750 | k | − | 5000 | ( | 1 | + | k | ) | × | 2 25 | × | 1 5 | = | 0 |
| 方程左边 = | 1750 | k | − | 80 | ( | 1 | + | k | ) |
| 1750 | k | − | 80 | ( | 1 | + | k | ) | = | 0 |
| 方程左边 = | 1750 | k | − | 80 | × | 1 | − | 80 | k |
| = | 1750 | k | − | 80 | − | 80 | k |
| = | 1670 | k | − | 80 |
| 1670 | k | − | 80 | = | 0 |
| 1670 | k | = | 0 | + | 80 |
| 1670 | k | = | 80 |
| k | = | 80 | ÷ | 1670 |
| = | 80 | × | 1 1670 |
| = | 8 | × | 1 167 |
| k | = | 8 167 |
| k | = | 0.047904 |