| ( | 10 | − | X | ) | ÷ | ( | 10 | − | 15 | ) | = | 8300 | ÷ | 12210 |
| Multiply both sides of the equation by: | ( | 10 | − | 15 | ) |
| ( | 10 | − | X | ) | = | 8300 | ÷ | 12210 | × | ( | 10 | − | 15 | ) |
| 10 | − | X | = | 8300 | ÷ | 12210 | × | ( | 10 | − | 15 | ) |
| 10 | − | X | = | 8300 | ÷ | 12210 | × | 10 | − | 8300 | ÷ | 12210 | × | 15 |
| 10 | − | X | = | 8300 1221 | − | 4150 407 |
| 10 | − | X | = | - | 4150 1221 |
| - | X | = | - | 4150 1221 | − | 10 |
| - | X | = | - | 16360 1221 |
16360 1221 | = | X |
| X | = | 16360 1221 |