| ( | 56 | + | X | ) | ÷ | ( | 80 | + | X | ) | = | 7 10 |
| Multiply both sides of the equation by: | ( | 80 | + | X | ) |
| ( | 56 | + | X | ) | = | 7 10 | ( | 80 | + | X | ) |
| 56 | + | X | = | 7 10 | ( | 80 | + | X | ) |
| 56 | + | X | = | 7 10 | × | 80 | + | 7 10 | X |
| 56 | + | X | = | 56 | + | 7 10 | X |
| X | − | 7 10 | X | = | 56 | − | 56 |
3 10 | X | = | 56 | − | 56 |
3 10 | X | = | 0 |
| X | = | 0 | ÷ | 3 10 |
| = | 0 | × | 10 3 |
| X | = | 0 |