| ( | 7 2 | ( | 3 2 | x | + | x | ) | − | 70 | ) | ÷ | 2 | = | 7 2 | x |
| 方程左边 = | 7 2 | ( | 3 2 | x | + | x | ) | × | 1 2 | − | 70 | × | 1 2 |
| = | 7 4 | ( | 3 2 | x | + | x | ) | − | 35 |
| = | 7 4 | × | 3 2 | x | + | 7 4 | x | − | 35 |
| = | 21 8 | x | + | 7 4 | x | − | 35 |
| = | 35 8 | x | − | 35 |
35 8 | x | − | 35 | = | 7 2 | x |
35 8 | x | − | 7 2 | x | = | 35 |
7 8 | x | = | 35 |
| x | = | 35 | ÷ | 7 8 |
| = | 35 | × | 8 7 |
| = | 5 | × | 8 |
| x | = | 40 |