| ( | X | + | 600 | ) | ÷ | ( | 1200 | + | X | ) | = | 3 4 |
| Multiply both sides of the equation by: | ( | 1200 | + | X | ) |
| ( | X | + | 600 | ) | = | 3 4 | ( | 1200 | + | X | ) |
| X | + | 600 | = | 3 4 | ( | 1200 | + | X | ) |
| X | + | 600 | = | 3 4 | × | 1200 | + | 3 4 | X |
| X | + | 600 | = | 900 | + | 3 4 | X |
| X | − | 3 4 | X | = | 900 | − | 600 |
1 4 | X | = | 900 | − | 600 |
1 4 | X | = | 300 |
| X | = | 300 | ÷ | 1 4 |
| = | 300 | × | 4 |
| X | = | 1200 |