| ( | 5 | X | + | 8 | ) | − | ( | X | + | 8 | ) | = | ( | 3 | X | − | 8 | ) | − | ( | X | − | 8 | ) |
| 方程左边 = | 5 | X | + | 8 | − | ( | X | + | 8 | ) |
| = | 5 | X | + | 8 | − | X | − | 8 |
| = | 4 | X | + | 0 |
| 4 | X | = | ( | 3 | X | − | 8 | ) | − | ( | X | − | 8 | ) |
| 方程右边 = | 3 | X | − | 8 | − | ( | X | − | 8 | ) |
| = | 3 | X | − | 8 | − | X | + | 8 |
| = | 2 | X | − | 0 |
| 4 | X | = | 2 | X | − | 0 |
| 4 | X | − | 2 | X | = | 0 |
| 2 | X | = | 0 |
| X | = | 0 | ÷ | 2 |
| = | 0 | × | 1 2 |
| X | = | 0 |