| ( | 32 | − | 2 | x | ) | ( | 20 | − | x | ) | = | 570 |
| Left side of the equation = | 32 | ( | 20 | − | x | ) | − | 2 | x | ( | 20 | − | x | ) |
| = | 32 | × | 20 | − | 32 | x | − | 2 | x | ( | 20 | − | x | ) |
| = | 640 | − | 32 | x | − | 2 | x | ( | 20 | − | x | ) |
| = | 640 | − | 32 | x | − | 2 | x | × | 20 | + | 2 | x | x |
| = | 640 | − | 32 | x | − | 40 | x | + | 2 | x | x |
| = | 640 | − | 72 | x | + | 2 | x | x |
| 640 | − | 72 | x | + | 2 | x | x | = | 570 |