| ( | 54 | + | x | ) | ÷ | ( | x | + | 72 | ) | = | 9 10 |
| Multiply both sides of the equation by: | ( | x | + | 72 | ) |
| ( | 54 | + | x | ) | = | 9 10 | ( | x | + | 72 | ) |
| 54 | + | x | = | 9 10 | ( | x | + | 72 | ) |
| 54 | + | x | = | 9 10 | x | + | 9 10 | × | 72 |
| 54 | + | x | = | 9 10 | x | + | 324 5 |
| x | − | 9 10 | x | = | 324 5 | − | 54 |
1 10 | x | = | 324 5 | − | 54 |
1 10 | x | = | 54 5 |
| x | = | 54 5 | ÷ | 1 10 |
| = | 54 5 | × | 10 |
| = | 54 | × | 2 |
| x | = | 108 |