| 6 | ( | x | − | 10 | ) | + | 15 | = | 2 | ( | x | + | 5 | ) | + | 25 |
| 方程左边 = | 6 | x | − | 6 | × | 10 | + | 15 |
| = | 6 | x | − | 60 | + | 15 |
| = | 6 | x | − | 45 |
| 6 | x | − | 45 | = | 2 | ( | x | + | 5 | ) | + | 25 |
| 方程右边 = | 2 | x | + | 2 | × | 5 | + | 25 |
| = | 2 | x | + | 10 | + | 25 |
| = | 2 | x | + | 35 |
| 6 | x | − | 45 | = | 2 | x | + | 35 |
| 6 | x | − | 2 | x | = | 35 | + | 45 |
| 4 | x | = | 35 | + | 45 |
| 4 | x | = | 80 |
| x | = | 80 | ÷ | 4 |
| = | 80 | × | 1 4 |
| = | 20 | × | 1 |
| x | = | 20 |