| ( | 300 | ÷ | x | ) | = | ( | 300 | ÷ | x | + | 5 | ) | + | 2 |
| 300 | ÷ | x | = | ( | 300 | ÷ | x | + | 5 | ) | + | 2 |
| 300 | ÷ | x | = | 300 | ÷ | x | + | 5 | + | 2 |
| 300 | ÷ | x | = | 300 | ÷ | x | + | 7 |
| 方程两边同时乘以: | x |
| 300 | = | 300 | ÷ | 1 | × | 1 | + | 7 | x |
| - | 7 | x | = | 300 | ÷ | 1 | × | 1 | − | 300 |
| - | 7 | x | = | 300 | − | 300 |
| - | 7 | x | = | 0 |
| - | 0 | = | 7 | x |
| 7 | x | = | - | 0 |
| x | = | - | 0 | ÷ | 7 |
| = | - | 0 | × | 1 7 |
| x | = | 0 |
| x | = | 0 |