| ( | X | + | 249 | ) | ÷ | ( | X | + | 713 | ) | = | 1 2 |
| 方程两边同时乘以: | ( | X | + | 713 | ) |
| ( | X | + | 249 | ) | = | 1 2 | ( | X | + | 713 | ) |
| X | + | 249 | = | 1 2 | ( | X | + | 713 | ) |
| X | + | 249 | = | 1 2 | X | + | 1 2 | × | 713 |
| X | + | 249 | = | 1 2 | X | + | 713 2 |
| X | − | 1 2 | X | = | 713 2 | − | 249 |
1 2 | X | = | 713 2 | − | 249 |
1 2 | X | = | 215 2 |
| X | = | 215 2 | ÷ | 1 2 |
| = | 215 2 | × | 2 |
| = | 215 | × | 1 |
| X | = | 215 |