| ( | X | + | 150 | ) | ÷ | ( | X | + | 400 | ) | = | 1 2 |
| Multiply both sides of the equation by: | ( | X | + | 400 | ) |
| ( | X | + | 150 | ) | = | 1 2 | ( | X | + | 400 | ) |
| X | + | 150 | = | 1 2 | ( | X | + | 400 | ) |
| X | + | 150 | = | 1 2 | X | + | 1 2 | × | 400 |
| X | + | 150 | = | 1 2 | X | + | 200 |
| X | − | 1 2 | X | = | 200 | − | 150 |
1 2 | X | = | 200 | − | 150 |
1 2 | X | = | 50 |
| X | = | 50 | ÷ | 1 2 |
| = | 50 | × | 2 |
| X | = | 100 |