| ( | 7 | + | X | ) | ÷ | ( | 10 | + | X | ) | = | 22 25 |
| 方程两边同时乘以: | ( | 10 | + | X | ) |
| ( | 7 | + | X | ) | = | 22 25 | ( | 10 | + | X | ) |
| 7 | + | X | = | 22 25 | ( | 10 | + | X | ) |
| 7 | + | X | = | 22 25 | × | 10 | + | 22 25 | X |
| 7 | + | X | = | 44 5 | + | 22 25 | X |
| X | − | 22 25 | X | = | 44 5 | − | 7 |
3 25 | X | = | 44 5 | − | 7 |
3 25 | X | = | 9 5 |
| X | = | 9 5 | ÷ | 3 25 |
| = | 9 5 | × | 25 3 |
| = | 3 | × | 5 |
| X | = | 15 |