| ( | 80 | − | x | ) | ÷ | ( | 40 | − | x | ) | = | 5 |
| Multiply both sides of the equation by: | ( | 40 | − | x | ) |
| ( | 80 | − | x | ) | = | 5 | ( | 40 | − | x | ) |
| 80 | − | x | = | 5 | ( | 40 | − | x | ) |
| 80 | − | x | = | 5 | × | 40 | − | 5 | x |
| 80 | − | x | = | 200 | − | 5 | x |
| - | x | + | 5 | x | = | 200 | − | 80 |
| 4 | x | = | 200 | − | 80 |
| 4 | x | = | 120 |
| x | = | 120 | ÷ | 4 |
| = | 120 | × | 1 4 |
| = | 30 | × | 1 |
| x | = | 30 |