| ( | 70 | − | 65 | ) | ÷ | ( | - | 56 | ) | = | ( | 70 | − | X | ) | ÷ | ( | X | − | 56 | ) |
| 方程两边同时乘以: | ( | - | 56 | ) | , | ( | X | − | 56 | ) |
| ( | 70 | − | 65 | ) | ( | X | − | 56 | ) | = | ( | 70 | − | X | ) | ( | - | 56 | ) |
| 70 | ( | X | − | 56 | ) | − | 65 | ( | X | − | 56 | ) | = | ( | 70 | − | X | ) | ( | - | 56 | ) |
| 70 | ( | X | − | 56 | ) | − | 65 | ( | X | − | 56 | ) | = | 70 | ( | - | 56 | ) | − | X | ( | - | 56 | ) |
| 70 | X | − | 70 | × | 56 | − | 65 | ( | X | − | 56 | ) | = | 70 | ( | - | 56 | ) | − | X | ( | - | 56 | ) |
| 70 | X | − | 70 | × | 56 | − | 65 | ( | X | − | 56 | ) | = | - | 70 | × | 56 | − | X | ( | - | 56 | ) |
| 70 | X | − | 3920 | − | 65 | ( | X | − | 56 | ) | = | - | 3920 | − | X | ( | - | 56 | ) |
| 70 | X | − | 3920 | − | 65 | X | + | 65 | × | 56 | = | - | 3920 | − | X | ( | - | 56 | ) |
| 70 | X | − | 3920 | − | 65 | X | + | 65 | × | 56 | = | - | 3920 | + | X | × | 56 |
| 70 | X | − | 3920 | − | 65 | X | + | 3640 | = | - | 3920 | + | X | × | 56 |
| 5 | X | − | 280 | = | - | 3920 | + | 56 | X |
| 5 | X | − | 56 | X | = | - | 3920 | + | 280 |
| - | 51 | X | = | - | 3920 | + | 280 |
| - | 51 | X | = | - | 3640 |
| 3640 | = | 51 | X |
| 51 | X | = | 3640 |
| X | = | 3640 | ÷ | 51 |
| = | 3640 | × | 1 51 |
| X | = | 3640 51 |
| X | = | 71.372549 |