| 600 | ÷ | x | = | 900 | ÷ | ( | x | + | 1 20 | ) |
| Multiply both sides of the equation by: | x | , | ( | x | + | 1 20 | ) |
| 600 | ( | x | + | 1 20 | ) | = | 900 | x |
| 600 | x | + | 600 | × | 1 20 | = | 900 | x |
| 600 | x | + | 30 | = | 900 | x |
| 600 | x | − | 900 | x | = | - | 30 |
| - | 300 | x | = | - | 30 |
| 30 | = | 300 | x |
| 300 | x | = | 30 |
| x | = | 30 | ÷ | 300 |
| = | 30 | × | 1 300 |
| = | 1 | × | 1 10 |
| x | = | 1 10 |
| x | = | 0.1 |