| 80000 | ÷ | ( | x | + | 400 | ) | = | 64000 | ÷ | x |
| Multiply both sides of the equation by: | ( | x | + | 400 | ) | , | x |
| 80000 | x | = | 64000 | ( | x | + | 400 | ) |
| 80000 | x | = | 64000 | x | + | 64000 | × | 400 |
| 80000 | x | = | 64000 | x | + | 25600000 |
| 80000 | x | − | 64000 | x | = | 25600000 |
| 16000 | x | = | 25600000 |
| x | = | 25600000 | ÷ | 16000 |
| = | 25600000 | × | 1 16000 |
| = | 1600 | × | 1 |
| x | = | 1600 |