| 20 | ( | 2 | − | x | ) | = | 200 | ( | 1 | − | x | ) |
| 方程左边 = | 20 | × | 2 | − | 20 | x |
| = | 40 | − | 20 | x |
| 40 | − | 20 | x | = | 200 | ( | 1 | − | x | ) |
| 方程右边 = | 200 | × | 1 | − | 200 | x |
| = | 200 | − | 200 | x |
| 40 | − | 20 | x | = | 200 | − | 200 | x |
| - | 20 | x | + | 200 | x | = | 200 | − | 40 |
| 180 | x | = | 200 | − | 40 |
| 180 | x | = | 160 |
| x | = | 160 | ÷ | 180 |
| = | 160 | × | 1 180 |
| = | 8 | × | 1 9 |
| x | = | 8 9 |
| x | = | 0.888889 |