| X | × | 600 | ÷ | ( | ( | 1 | − | X | ) | × | 1800 | ) | = | 1 20 |
| 方程两边同时乘以: | ( | ( | 1 | − | X | ) | × | 1800 | ) |
| X | × | 600 | = | 1 20 | ( | ( | 1 | − | X | ) | × | 1800 | ) |
| X | × | 600 | = | 1 20 | ( | 1 | − | X | ) | × | 1800 |
| X | × | 600 | = | 90 | ( | 1 | − | X | ) |
| 600 | X | = | 90 | × | 1 | − | 90 | X |
| 600 | X | = | 90 | − | 90 | X |
| 600 | X | + | 90 | X | = | 90 |
| 690 | X | = | 90 |
| X | = | 90 | ÷ | 690 |
| = | 90 | × | 1 690 |
| = | 3 | × | 1 23 |
| X | = | 3 23 |
| X | = | 0.130435 |