| X | ÷ | ( | X | + | 300 | ) | × | 100 100 | = | 12 100 |
| 方程两边同时乘以: | ( | X | + | 300 | ) |
| X | × | 100 100 | = | 12 100 | ( | X | + | 300 | ) |
| X | × | 100 100 | = | 12 100 | X | + | 12 100 | × | 300 |
| X | × | 100 100 | = | 12 100 | X | + | 36 |
100 100 | X | − | 12 100 | X | = | 36 |
22 25 | X | = | 36 |
| X | = | 36 | ÷ | 22 25 |
| = | 36 | × | 25 22 |
| = | 18 | × | 25 11 |
| X | = | 450 11 |
| X | = | 40.909091 |