| ( | 100 | × | 30 100 | ) | ÷ | ( | 100 | + | X | + | X | ) | = | 20 100 |
| Multiply both sides of the equation by: | ( | 100 | + | X | + | X | ) |
| ( | 100 | × | 30 100 | ) | = | 20 100 | ( | 100 | + | X | + | X | ) |
| 100 | × | 30 100 | = | 20 100 | ( | 100 | + | X | + | X | ) |
| 100 | × | 30 100 | = | 20 100 | × | 100 | + | 20 100 | X | + | 20 100 | X |
| 30 | = | 20 | + | 20 100 | X | + | 20 100 | X |
| 30 | = | 20 | + | 2 5 | X |
| - | 2 5 | X | = | 20 | − | 30 |
| - | 2 5 | X | = | - | 10 |
| 10 | = | 2 5 | X |
2 5 | X | = | 10 |
| X | = | 10 | ÷ | 2 5 |
| = | 10 | × | 5 2 |
| = | 5 | × | 5 |
| X | = | 25 |