| ( | X | − | 85 | ) | ÷ | X | − | ( | X | − | 100 | ) | ÷ | X | = | 6 25 |
| Multiply both sides of the equation by: | X |
| ( | X | − | 85 | ) | − | ( | X | − | 100 | ) | ÷ | 1 | × | 1 | = | 6 25 | X |
| X | − | 85 | − | ( | X | − | 100 | ) | ÷ | 1 | × | 1 | = | 6 25 | X |
| X | − | 85 | − | ( | X | − | 100 | ) | × | 1 | = | 6 25 | X |
| X | − | 85 | − | X | × | 1 | + | 100 | × | 1 | = | 6 25 | X |
| X | − | 85 | − | X | × | 1 | + | 100 | = | 6 25 | X |
| 0 | X | + | 15 | = | 6 25 | X |
| - | 6 25 | X | = | - | 15 |
| 15 | = | 6 25 | X |
6 25 | X | = | 15 |
| X | = | 15 | ÷ | 6 25 |
| = | 15 | × | 25 6 |
| = | 5 | × | 25 2 |
| X | = | 125 2 |
| X | = | 62.5 |