| ( | 78 | + | X | ) | ÷ | ( | 78 | + | 74 | + | X | ) | = | 11 20 |
| Multiply both sides of the equation by: | ( | 78 | + | 74 | + | X | ) |
| ( | 78 | + | X | ) | = | 11 20 | ( | 78 | + | 74 | + | X | ) |
| 78 | + | X | = | 11 20 | ( | 78 | + | 74 | + | X | ) |
| 78 | + | X | = | 11 20 | × | 78 | + | 11 20 | × | 74 | + | 11 20 | X |
| 78 | + | X | = | 429 10 | + | 407 10 | + | 11 20 | X |
| 78 | + | X | = | 418 5 | + | 11 20 | X |
| X | − | 11 20 | X | = | 418 5 | − | 78 |
9 20 | X | = | 418 5 | − | 78 |
9 20 | X | = | 28 5 |
| X | = | 28 5 | ÷ | 9 20 |
| = | 28 5 | × | 20 9 |
| = | 28 | × | 4 9 |
| X | = | 112 9 |
| X | = | 12.444444 |