| ( | x | − | 41 | ) | ( | 16 | − | 120 | x | ) | = | 3640 |
| Left side of the equation = | x | ( | 16 | − | 120 | x | ) | − | 41 | ( | 16 | − | 120 | x | ) |
| = | x | × | 16 | − | x | × | 120 | x | − | 41 | ( | 16 | − | 120 | x | ) |
| = | 16 | x | − | x | × | 120 | x | − | 41 | × | 16 | + | 41 | × | 120 | x |
| = | 16 | x | − | x | × | 120 | x | − | 656 | + | 4920 | x |
| = | 4936 | x | − | x | × | 120 | x | − | 656 |
| 4936 | x | − | x | × | 120 | x | − | 656 | = | 3640 |