| 5 | ( | 3 | − | 2 | x | ) | − | 12 | ( | 5 | − | 2 | x | ) | = | - | 17 |
| 方程左边 = | 5 | × | 3 | − | 5 | × | 2 | x | − | 12 | ( | 5 | − | 2 | x | ) |
| = | 15 | − | 10 | x | − | 12 | ( | 5 | − | 2 | x | ) |
| = | 15 | − | 10 | x | − | 12 | × | 5 | + | 12 | × | 2 | x |
| = | 15 | − | 10 | x | − | 60 | + | 24 | x |
| = | - | 45 | + | 14 | x |
| - | 45 | + | 14 | x | = | - | 17 |
| 14 | x | = | - | 17 | + | 45 |
| 14 | x | = | 28 |
| x | = | 28 | ÷ | 14 |
| = | 28 | × | 1 14 |
| = | 2 | × | 1 |
| x | = | 2 |