| ( | 8 | X | − | 10 | ) | ÷ | 3 | − | 9 | X | ÷ | 5 | = | 30 |
| 方程左边 = | ( | 8 | X | − | 10 | ) | × | 1 3 | − | 9 5 | X |
| ( | 8 | X | − | 10 | ) | × | 1 3 | − | 9 5 | X | = | 30 |
| 方程左边 = | 8 | X | × | 1 3 | − | 10 | × | 1 3 | − | 9 5 | X |
| = | 8 3 | X | − | 10 3 | − | 9 5 | X |
| = | 13 15 | X | − | 10 3 |
13 15 | X | − | 10 3 | = | 30 |
13 15 | X | = | 30 | + | 10 3 |
13 15 | X | = | 100 3 |
| X | = | 100 3 | ÷ | 13 15 |
| = | 100 3 | × | 15 13 |
| = | 100 | × | 5 13 |
| X | = | 500 13 |
| X | = | 38.461538 |