| 200 | ÷ | X | = | 200 | ÷ | ( | X | + | 3 5 | ) | × | 4 |
| 方程两边同时乘以: | X | , | ( | X | + | 3 5 | ) |
| 200 | ( | X | + | 3 5 | ) | = | 200 | × | 4 | X |
| 200 | X | + | 200 | × | 3 5 | = | 200 | × | 4 | X |
| 200 | X | + | 120 | = | 800 | X |
| 200 | X | − | 800 | X | = | - | 120 |
| - | 600 | X | = | - | 120 |
| 120 | = | 600 | X |
| 600 | X | = | 120 |
| X | = | 120 | ÷ | 600 |
| = | 120 | × | 1 600 |
| = | 1 | × | 1 5 |
| X | = | 1 5 |
| X | = | 0.2 |