| ( | x | − | 500 | ) | × | 2 | = | ( | x | − | 800 | ) | × | 5 2 |
| 方程左边 = | x | × | 2 | − | 500 | × | 2 |
| = | x | × | 2 | − | 1000 |
| 2 | x | − | 1000 | = | ( | x | − | 800 | ) | × | 5 2 |
| 方程右边 = | x | × | 5 2 | − | 800 | × | 5 2 |
| = | x | × | 5 2 | − | 2000 |
| 2 | x | − | 1000 | = | 5 2 | x | − | 2000 |
| 2 | x | − | 5 2 | x | = | - | 2000 | + | 1000 |
| - | 1 2 | x | = | - | 2000 | + | 1000 |
| - | 1 2 | x | = | - | 1000 |
| 1000 | = | 1 2 | x |
1 2 | x | = | 1000 |
| x | = | 1000 | ÷ | 1 2 |
| = | 1000 | × | 2 |
| x | = | 2000 |