70 100 | × | 10 | x | − | 10 | ( | x | − | 45 | ) | = | ( | x | − | 25 | ) | × | 12 | − | 12 | ( | x | − | 45 | ) |
| 方程左边 = | 7 | x | − | 10 | ( | x | − | 45 | ) |
| 7 | x | − | 10 | ( | x | − | 45 | ) | = | ( | x | − | 25 | ) | × | 12 | − | 12 | ( | x | − | 45 | ) |
| 方程左边 = | 7 | x | − | 10 | x | + | 10 | × | 45 |
| = | 7 | x | − | 10 | x | + | 450 |
| = | - | 3 | x | + | 450 |
| - | 3 | x | + | 450 | = | ( | x | − | 25 | ) | × | 12 | − | 12 | ( | x | − | 45 | ) |
| 方程右边 = | x | × | 12 | − | 25 | × | 12 | − | 12 | ( | x | − | 45 | ) |
| = | x | × | 12 | − | 300 | − | 12 | ( | x | − | 45 | ) |
| = | 12 | x | − | 300 | − | 12 | x | + | 12 | × | 45 |
| = | 12 | x | − | 300 | − | 12 | x | + | 540 |
| = | 0 | x | + | 240 |
| - | 3 | x | + | 450 | = | 0 | x | + | 240 |
| - | 3 | x | = | 240 | − | 450 |
| - | 3 | x | = | - | 210 |
| 210 | = | 3 | x |
| 3 | x | = | 210 |
| x | = | 210 | ÷ | 3 |
| = | 210 | × | 1 3 |
| = | 70 | × | 1 |
| x | = | 70 |