| ( | X | + | 40 | ) | ÷ | ( | X | + | 60 | ) | = | 17 20 |
| Multiply both sides of the equation by: | ( | X | + | 60 | ) |
| ( | X | + | 40 | ) | = | 17 20 | ( | X | + | 60 | ) |
| X | + | 40 | = | 17 20 | ( | X | + | 60 | ) |
| X | + | 40 | = | 17 20 | X | + | 17 20 | × | 60 |
| X | + | 40 | = | 17 20 | X | + | 51 |
| X | − | 17 20 | X | = | 51 | − | 40 |
3 20 | X | = | 51 | − | 40 |
3 20 | X | = | 11 |
| X | = | 11 | ÷ | 3 20 |
| = | 11 | × | 20 3 |
| X | = | 220 3 |
| X | = | 73.333333 |