| 216 | ÷ | ( | x | + | 18 | ) | = | 72 | ÷ | ( | 12 | − | x | ) |
| Multiply both sides of the equation by: | ( | x | + | 18 | ) | , | ( | 12 | − | x | ) |
| 216 | ( | 12 | − | x | ) | = | 72 | ( | x | + | 18 | ) |
| 216 | × | 12 | − | 216 | x | = | 72 | ( | x | + | 18 | ) |
| 216 | × | 12 | − | 216 | x | = | 72 | x | + | 72 | × | 18 |
| 2592 | − | 216 | x | = | 72 | x | + | 1296 |
| - | 216 | x | − | 72 | x | = | 1296 | − | 2592 |
| - | 288 | x | = | 1296 | − | 2592 |
| - | 288 | x | = | - | 1296 |
| 1296 | = | 288 | x |
| 288 | x | = | 1296 |
| x | = | 1296 | ÷ | 288 |
| = | 1296 | × | 1 288 |
| = | 9 | × | 1 2 |
| x | = | 9 2 |
| x | = | 4.5 |