| 2 | ( | 2 | x | − | 1 | ) | − | 18 | = | 128 | − | 5 | ( | x | − | 1 | ) |
| Left side of the equation = | 2 | × | 2 | x | − | 2 | × | 1 | − | 18 |
| = | 4 | x | − | 2 | − | 18 |
| = | 4 | x | − | 20 |
| 4 | x | − | 20 | = | 128 | − | 5 | ( | x | − | 1 | ) |
| Right side of the equation = | 128 | − | 5 | x | + | 5 | × | 1 |
| = | 128 | − | 5 | x | + | 5 |
| = | 133 | − | 5 | x |
| 4 | x | − | 20 | = | 133 | − | 5 | x |
| 4 | x | + | 5 | x | = | 133 | + | 20 |
| 9 | x | = | 133 | + | 20 |
| 9 | x | = | 153 |
| x | = | 153 | ÷ | 9 |
| = | 153 | × | 1 9 |
| = | 17 | × | 1 |
| x | = | 17 |