| ( | 108 | + | x | ) | ÷ | ( | 200 | + | x | ) | = | 3 5 |
| Multiply both sides of the equation by: | ( | 200 | + | x | ) |
| ( | 108 | + | x | ) | = | 3 5 | ( | 200 | + | x | ) |
| 108 | + | x | = | 3 5 | ( | 200 | + | x | ) |
| 108 | + | x | = | 3 5 | × | 200 | + | 3 5 | x |
| 108 | + | x | = | 120 | + | 3 5 | x |
| x | − | 3 5 | x | = | 120 | − | 108 |
2 5 | x | = | 120 | − | 108 |
2 5 | x | = | 12 |
| x | = | 12 | ÷ | 2 5 |
| = | 12 | × | 5 2 |
| = | 6 | × | 5 |
| x | = | 30 |