| 3 | ( | 15 | + | x | ) | = | 5 | ( | 35 | + | x | ) |
| 方程左边 = | 3 | × | 15 | + | 3 | x |
| = | 45 | + | 3 | x |
| 45 | + | 3 | x | = | 5 | ( | 35 | + | x | ) |
| 方程右边 = | 5 | × | 35 | + | 5 | x |
| = | 175 | + | 5 | x |
| 45 | + | 3 | x | = | 175 | + | 5 | x |
| 3 | x | − | 5 | x | = | 175 | − | 45 |
| - | 2 | x | = | 175 | − | 45 |
| - | 2 | x | = | 130 |
| - | 130 | = | 2 | x |
| 2 | x | = | - | 130 |
| x | = | - | 130 | ÷ | 2 |
| = | - | 130 | × | 1 2 |
| = | - | 65 | × | 1 |
| x | = | - | 65 |