| ( | X | − | 20 100 | + | 40 | ) | ÷ | X | = | 28 | ÷ | 25 |
| 方程两边同时乘以: | X |
| ( | X | − | 20 100 | + | 40 | ) | = | 28 | ÷ | 25 | × | X |
| X | − | 20 100 | + | 40 | = | 28 | ÷ | 25 | × | X |
| X | − | 20 100 | + | 40 | = | 28 25 | X |
| X | + | 199 5 | = | 28 25 | X |
| X | − | 28 25 | X | = | - | 199 5 |
| - | 3 25 | X | = | - | 199 5 |
199 5 | = | 3 25 | X |
3 25 | X | = | 199 5 |
| X | = | 199 5 | ÷ | 3 25 |
| = | 199 5 | × | 25 3 |
| = | 199 | × | 5 3 |
| X | = | 995 3 |
| X | = | 331.666667 |