| ( | 40 | + | 10 | X | ) | ÷ | ( | 13 | + | X | ) | × | ( | 13 | + | X | ) | = | 0 |
| Multiply both sides of the equation by: | ( | 13 | + | X | ) |
| ( | 40 | + | 10 | X | ) | ( | 13 | + | X | ) | = | 0 |
| 40 | ( | 13 | + | X | ) | + | 10 | X | ( | 13 | + | X | ) | = | 0 |
| 40 | × | 13 | + | 40 | X | + | 10 | X | ( | 13 | + | X | ) | = | 0 |
| 520 | + | 40 | X | + | 10 | X | ( | 13 | + | X | ) | = | 0 |
| 520 | + | 40 | X | + | 10 | X | × | 13 | + | 10 | X | X | = | 0 |
| 520 | + | 40 | X | + | 130 | X | + | 10 | X | X | = | 0 |
| 520 | + | 170 | X | + | 10 | X | X | = | 0 |