| 300 | ÷ | ( | x | − | 4 | ) | = | 400 | ÷ | x |
| Multiply both sides of the equation by: | ( | x | − | 4 | ) | , | x |
| 300 | x | = | 400 | ( | x | − | 4 | ) |
| 300 | x | = | 400 | x | − | 400 | × | 4 |
| 300 | x | = | 400 | x | − | 1600 |
| 300 | x | − | 400 | x | = | - | 1600 |
| - | 100 | x | = | - | 1600 |
| 1600 | = | 100 | x |
| 100 | x | = | 1600 |
| x | = | 1600 | ÷ | 100 |
| = | 1600 | × | 1 100 |
| = | 16 | × | 1 |
| x | = | 16 |