| 150 | x | = | ( | 150 | + | 30 | ) | ( | x | − | 10 | ) |
| 方程右边 = | 150 | ( | x | − | 10 | ) | + | 30 | ( | x | − | 10 | ) |
| = | 150 | x | − | 150 | × | 10 | + | 30 | ( | x | − | 10 | ) |
| = | 150 | x | − | 1500 | + | 30 | ( | x | − | 10 | ) |
| = | 150 | x | − | 1500 | + | 30 | x | − | 30 | × | 10 |
| = | 150 | x | − | 1500 | + | 30 | x | − | 300 |
| = | 180 | x | − | 1800 |
| 150 | x | = | 180 | x | − | 1800 |
| 150 | x | − | 180 | x | = | - | 1800 |
| - | 30 | x | = | - | 1800 |
| 1800 | = | 30 | x |
| 30 | x | = | 1800 |
| x | = | 1800 | ÷ | 30 |
| = | 1800 | × | 1 30 |
| = | 60 | × | 1 |
| x | = | 60 |