| ( | 266 | + | X | ) | ÷ | ( | 31 | + | X | ) | = | 13 100 |
| Multiply both sides of the equation by: | ( | 31 | + | X | ) |
| ( | 266 | + | X | ) | = | 13 100 | ( | 31 | + | X | ) |
| 266 | + | X | = | 13 100 | ( | 31 | + | X | ) |
| 266 | + | X | = | 13 100 | × | 31 | + | 13 100 | X |
| 266 | + | X | = | 403 100 | + | 13 100 | X |
| X | − | 13 100 | X | = | 403 100 | − | 266 |
87 100 | X | = | 403 100 | − | 266 |
87 100 | X | = | - | 26197 100 |
| X | = | - | 26197 100 | ÷ | 87 100 |
| = | - | 26197 100 | × | 100 87 |
| = | - | 26197 | × | 1 87 |
| X | = | - | 26197 87 |
| X | = | - 301.114943 |