| ( | 7 10 | + | x | ) | ÷ | 2 | × | 9 2 | × | 30 | = | 0 |
| 方程左边 = | ( | 7 10 | + | x | ) | × | 135 2 |
| ( | 7 10 | + | x | ) | × | 135 2 | = | 0 |
| 方程左边 = | 7 10 | × | 135 2 | + | x | × | 135 2 |
| = | 189 4 | + | x | × | 135 2 |
189 4 | + | 135 2 | x | = | 0 |
135 2 | x | = | 0 | − | 189 4 |
135 2 | x | = | - | 189 4 |
| x | = | - | 189 4 | ÷ | 135 2 |
| = | - | 189 4 | × | 2 135 |
| = | - | 7 2 | × | 1 5 |
| x | = | - | 7 10 |
| x | = | - 0.7 |