| ( | 500 | − | X | ) | ÷ | X | × | 100 | = | 91 10 |
| Multiply both sides of the equation by: | X |
| ( | 500 | − | X | ) | × | 100 | = | 91 10 | X |
| 500 | × | 100 | − | X | × | 100 | = | 91 10 | X |
| 50000 | − | X | × | 100 | = | 91 10 | X |
| - | 100 | X | − | 91 10 | X | = | - | 50000 |
| - | 1091 10 | X | = | - | 50000 |
| 50000 | = | 1091 10 | X |
1091 10 | X | = | 50000 |
| X | = | 50000 | ÷ | 1091 10 |
| = | 50000 | × | 10 1091 |
| X | = | 500000 1091 |
| X | = | 458.295142 |