| ( | x | − | 20 | ) | ( | 2 | x | − | 80 | ) | = | - | 150 |
| Left side of the equation = | x | ( | 2 | x | − | 80 | ) | − | 20 | ( | 2 | x | − | 80 | ) |
| = | x | × | 2 | x | − | x | × | 80 | − | 20 | ( | 2 | x | − | 80 | ) |
| = | x | × | 2 | x | − | 80 | x | − | 20 | × | 2 | x | + | 20 | × | 80 |
| = | x | × | 2 | x | − | 80 | x | − | 40 | x | + | 1600 |
| = | x | × | 2 | x | − | 120 | x | + | 1600 |
| x | × | 2 | x | − | 120 | x | + | 1600 | = | - | 150 |