| 12 | + | ( | 5 | − | X | ) | ÷ | ( | 5 | − | X | ) | = | 3 10 |
| 方程两边同时乘以: | ( | 5 | − | X | ) |
| 12 | ( | 5 | − | X | ) | + | ( | 5 | − | X | ) | = | 3 10 | ( | 5 | − | X | ) |
| 12 | × | 5 | − | 12 | X | + | ( | 5 | − | X | ) | = | 3 10 | ( | 5 | − | X | ) |
| 12 | × | 5 | − | 12 | X | + | ( | 5 | − | X | ) | = | 3 10 | × | 5 | − | 3 10 | X |
| 60 | − | 12 | X | + | ( | 5 | − | X | ) | = | 3 2 | − | 3 10 | X |
| 60 | − | 12 | X | + | 5 | − | X | = | 3 2 | − | 3 10 | X |
| 65 | − | 13 | X | = | 3 2 | − | 3 10 | X |
| - | 13 | X | + | 3 10 | X | = | 3 2 | − | 65 |
| - | 127 10 | X | = | 3 2 | − | 65 |
| - | 127 10 | X | = | - | 127 2 |
127 2 | = | 127 10 | X |
127 10 | X | = | 127 2 |
| X | = | 127 2 | ÷ | 127 10 |
| = | 127 2 | × | 10 127 |
| = | 127 | × | 5 127 |
| X | = | 635 127 |
| X | = | 635 127 |