| ( | 240 | − | x | ) | ÷ | ( | 100 | − | x | ) | = | 3 |
| Multiply both sides of the equation by: | ( | 100 | − | x | ) |
| ( | 240 | − | x | ) | = | 3 | ( | 100 | − | x | ) |
| 240 | − | x | = | 3 | ( | 100 | − | x | ) |
| 240 | − | x | = | 3 | × | 100 | − | 3 | x |
| 240 | − | x | = | 300 | − | 3 | x |
| - | x | + | 3 | x | = | 300 | − | 240 |
| 2 | x | = | 300 | − | 240 |
| 2 | x | = | 60 |
| x | = | 60 | ÷ | 2 |
| = | 60 | × | 1 2 |
| = | 30 | × | 1 |
| x | = | 30 |