| 300 | ÷ | x | − | 3 | = | 300 | ÷ | ( | 4 | ÷ | 5 | × | x | ) |
| 方程两边同时乘以: | x | , | ( | 4 | ÷ | 5 | × | 1 | ) |
| 300 | ( | 4 | ÷ | 5 | × | 1 | ) | − | 3 | x | ( | 4 | ÷ | 5 | × | 1 | ) | = | 300 | × | 1 |
| 300 | × | 4 | ÷ | 5 | × | 1 | − | 3 | x | ( | 4 | ÷ | 5 | × | 1 | ) | = | 300 | × | 1 |
| 240 | − | 3 | x | ( | 4 | ÷ | 5 | × | 1 | ) | = | 300 |
| 240 | − | 3 | x | × | 4 | ÷ | 5 | × | 1 | = | 300 |
| 240 | − | 12 5 | x | = | 300 |
| - | 12 5 | x | = | 300 | − | 240 |
| - | 12 5 | x | = | 60 |
| - | 60 | = | 12 5 | x |
12 5 | x | = | - | 60 |
| x | = | - | 60 | ÷ | 12 5 |
| = | - | 60 | × | 5 12 |
| = | - | 5 | × | 5 |
| x | = | - | 25 |