9 2 | = | ( | 5 | X | + | 86 | ) | ÷ | ( | X | + | 21 | ) |
| 方程两边同时乘以: | ( | X | + | 21 | ) |
9 2 | ( | X | + | 21 | ) | = | ( | 5 | X | + | 86 | ) |
9 2 | X | + | 9 2 | × | 21 | = | ( | 5 | X | + | 86 | ) |
9 2 | X | + | 9 2 | × | 21 | = | 5 | X | + | 86 |
9 2 | X | + | 189 2 | = | 5 | X | + | 86 |
9 2 | X | − | 5 | X | = | 86 | − | 189 2 |
| - | 1 2 | X | = | 86 | − | 189 2 |
| - | 1 2 | X | = | - | 17 2 |
17 2 | = | 1 2 | X |
1 2 | X | = | 17 2 |
| X | = | 17 2 | ÷ | 1 2 |
| = | 17 2 | × | 2 |
| = | 17 | × | 1 |
| X | = | 17 |