| x | ÷ | ( | x | + | 1600 | ) | × | 100 100 | = | 20 100 |
| Multiply both sides of the equation by: | ( | x | + | 1600 | ) |
| x | × | 100 100 | = | 20 100 | ( | x | + | 1600 | ) |
| x | × | 100 100 | = | 20 100 | x | + | 20 100 | × | 1600 |
| x | × | 100 100 | = | 20 100 | x | + | 320 |
100 100 | x | − | 20 100 | x | = | 320 |
4 5 | x | = | 320 |
| x | = | 320 | ÷ | 4 5 |
| = | 320 | × | 5 4 |
| = | 80 | × | 5 |
| x | = | 400 |