| ( | 10 | + | X | ) | ÷ | ( | 31 | + | X | ) | = | 4 5 |
| Multiply both sides of the equation by: | ( | 31 | + | X | ) |
| ( | 10 | + | X | ) | = | 4 5 | ( | 31 | + | X | ) |
| 10 | + | X | = | 4 5 | ( | 31 | + | X | ) |
| 10 | + | X | = | 4 5 | × | 31 | + | 4 5 | X |
| 10 | + | X | = | 124 5 | + | 4 5 | X |
| X | − | 4 5 | X | = | 124 5 | − | 10 |
1 5 | X | = | 124 5 | − | 10 |
1 5 | X | = | 74 5 |
| X | = | 74 5 | ÷ | 1 5 |
| = | 74 5 | × | 5 |
| = | 74 | × | 1 |
| X | = | 74 |