| 900 | ÷ | x | − | 400 | ÷ | x | − | 5 | = | 100 |
| 方程两边同时乘以: | x |
| 900 | − | 400 | ÷ | 1 | × | 1 | − | 5 | x | = | 100 | x |
| - | 5 | x | − | 100 | x | = | - | 900 | + | 400 | ÷ | 1 | × | 1 |
| - | 5 | x | − | 100 | x | = | - | 900 | + | 400 |
| - | 105 | x | = | - | 900 | + | 400 |
| - | 105 | x | = | - | 500 |
| 500 | = | 105 | x |
| 105 | x | = | 500 |
| x | = | 500 | ÷ | 105 |
| = | 500 | × | 1 105 |
| = | 100 | × | 1 21 |
| x | = | 100 21 |
| x | = | 4.761905 |