| 45 | X | = | ( | 45 | + | 9 | ) | ( | X | − | 3 | ) |
| Right side of the equation = | 45 | ( | X | − | 3 | ) | + | 9 | ( | X | − | 3 | ) |
| = | 45 | X | − | 45 | × | 3 | + | 9 | ( | X | − | 3 | ) |
| = | 45 | X | − | 135 | + | 9 | ( | X | − | 3 | ) |
| = | 45 | X | − | 135 | + | 9 | X | − | 9 | × | 3 |
| = | 45 | X | − | 135 | + | 9 | X | − | 27 |
| = | 54 | X | − | 162 |
| 45 | X | = | 54 | X | − | 162 |
| 45 | X | − | 54 | X | = | - | 162 |
| - | 9 | X | = | - | 162 |
| 162 | = | 9 | X |
| 9 | X | = | 162 |
| X | = | 162 | ÷ | 9 |
| = | 162 | × | 1 9 |
| = | 18 | × | 1 |
| X | = | 18 |