12 5 | + | 9 100 | ( | X | − | 20 | ) | = | 1 10 | X |
| Left side of the equation = | 12 5 | + | 9 100 | X | − | 9 100 | × | 20 |
| = | 12 5 | + | 9 100 | X | − | 9 5 |
| = | 3 5 | + | 9 100 | X |
3 5 | + | 9 100 | X | = | 1 10 | X |
9 100 | X | − | 1 10 | X | = | - | 3 5 |
| - | 1 100 | X | = | - | 3 5 |
3 5 | = | 1 100 | X |
1 100 | X | = | 3 5 |
| X | = | 3 5 | ÷ | 1 100 |
| = | 3 5 | × | 100 |
| = | 3 | × | 20 |
| X | = | 60 |