| ( | x | − | 80 | ) | × | 7 10 | = | ( | 3 | + | x | − | 70 | ) | × | 3 5 |
| 方程左边 = | x | × | 7 10 | − | 80 | × | 7 10 |
| = | x | × | 7 10 | − | 56 |
7 10 | x | − | 56 | = | ( | 3 | + | x | − | 70 | ) | × | 3 5 |
| 方程右边 = | 3 | × | 3 5 | + | x | × | 3 5 | − | 70 | × | 3 5 |
| = | 9 5 | + | x | × | 3 5 | − | 42 |
| = | - | 201 5 | + | 3 5 | x |
7 10 | x | − | 56 | = | - | 201 5 | + | 3 5 | x |
7 10 | x | − | 3 5 | x | = | - | 201 5 | + | 56 |
1 10 | x | = | - | 201 5 | + | 56 |
1 10 | x | = | 79 5 |
| x | = | 79 5 | ÷ | 1 10 |
| = | 79 5 | × | 10 |
| = | 79 | × | 2 |
| x | = | 158 |