| 1800 | ÷ | x | = | 1800 | ÷ | ( | 6 5 | x | ) | + | 15 |
| Multiply both sides of the equation by: | x | , | ( | 6 5 | × | 1 | ) |
| 1800 | ( | 6 5 | × | 1 | ) | = | 1800 | × | 1 | + | 15 | x | ( | 6 5 | × | 1 | ) |
| 1800 | × | 6 5 | × | 1 | = | 1800 | × | 1 | + | 15 | x | ( | 6 5 | × | 1 | ) |
| 1800 | × | 6 5 | × | 1 | = | 1800 | × | 1 | + | 15 | x | × | 6 5 | × | 1 |
| 2160 | = | 1800 | + | 18 | x |
| - | 18 | x | = | 1800 | − | 2160 |
| - | 18 | x | = | - | 360 |
| 360 | = | 18 | x |
| 18 | x | = | 360 |
| x | = | 360 | ÷ | 18 |
| = | 360 | × | 1 18 |
| = | 20 | × | 1 |
| x | = | 20 |