| 2 | x | + | ( | x | − | 70 | ) | + | ( | x | − | 60 | ) | + | ( | x | − | 30 | ) | = | 225 |
| 方程左边 = | 2 | x | + | x | − | 70 | + | ( | x | − | 60 | ) | + | ( | x | − | 30 | ) |
| = | 3 | x | − | 70 | + | ( | x | − | 60 | ) | + | ( | x | − | 30 | ) |
| = | 3 | x | − | 70 | + | x | − | 60 | + | ( | x | − | 30 | ) |
| = | 4 | x | − | 130 | + | ( | x | − | 30 | ) |
| = | 4 | x | − | 130 | + | x | − | 30 |
| = | 5 | x | − | 160 |
| 5 | x | − | 160 | = | 225 |
| 5 | x | = | 225 | + | 160 |
| 5 | x | = | 385 |
| x | = | 385 | ÷ | 5 |
| = | 385 | × | 1 5 |
| = | 77 | × | 1 |
| x | = | 77 |