| 200 | ( | X | − | 3 | ) | = | 150 | ( | X | + | 2 | ) |
| 方程左边 = | 200 | X | − | 200 | × | 3 |
| = | 200 | X | − | 600 |
| 200 | X | − | 600 | = | 150 | ( | X | + | 2 | ) |
| 方程右边 = | 150 | X | + | 150 | × | 2 |
| = | 150 | X | + | 300 |
| 200 | X | − | 600 | = | 150 | X | + | 300 |
| 200 | X | − | 150 | X | = | 300 | + | 600 |
| 50 | X | = | 300 | + | 600 |
| 50 | X | = | 900 |
| X | = | 900 | ÷ | 50 |
| = | 900 | × | 1 50 |
| = | 18 | × | 1 |
| X | = | 18 |