| 60 | ( | 3 | + | x | ) | = | 55 | ( | 2 | + | x | ) | + | 30 | × | 3 |
| 方程左边 = | 60 | × | 3 | + | 60 | x |
| = | 180 | + | 60 | x |
| 180 | + | 60 | x | = | 55 | ( | 2 | + | x | ) | + | 30 | × | 3 |
| 方程右边 = | 55 | ( | 2 | + | x | ) | + | 90 |
| 180 | + | 60 | x | = | 55 | ( | 2 | + | x | ) | + | 90 |
| 方程右边 = | 55 | × | 2 | + | 55 | x | + | 90 |
| = | 110 | + | 55 | x | + | 90 |
| = | 200 | + | 55 | x |
| 180 | + | 60 | x | = | 200 | + | 55 | x |
| 60 | x | − | 55 | x | = | 200 | − | 180 |
| 5 | x | = | 200 | − | 180 |
| 5 | x | = | 20 |
| x | = | 20 | ÷ | 5 |
| = | 20 | × | 1 5 |
| = | 4 | × | 1 |
| x | = | 4 |