3 10 | ( | 20 | + | x | ) | = | 1 2 | ( | 20 | + | x | ) |
| 方程左边 = | 3 10 | × | 20 | + | 3 10 | x |
| = | 6 | + | 3 10 | x |
| 6 | + | 3 10 | x | = | 1 2 | ( | 20 | + | x | ) |
| 方程右边 = | 1 2 | × | 20 | + | 1 2 | x |
| = | 10 | + | 1 2 | x |
| 6 | + | 3 10 | x | = | 10 | + | 1 2 | x |
3 10 | x | − | 1 2 | x | = | 10 | − | 6 |
| - | 1 5 | x | = | 10 | − | 6 |
| - | 1 5 | x | = | 4 |
| - | 4 | = | 1 5 | x |
1 5 | x | = | - | 4 |
| x | = | - | 4 | ÷ | 1 5 |
| = | - | 4 | × | 5 |
| x | = | - | 20 |