| ( | 6 | − | x | ) | ( | 12 | − | 2 | x | ) | ÷ | 2 | = | 80 |
| Left side of the equation = | 6 | ( | 12 | − | 2 | x | ) | × | 1 2 | − | x | ( | 12 | − | 2 | x | ) | × | 1 2 |
| = | 3 | ( | 12 | − | 2 | x | ) | − | x | ( | 12 | − | 2 | x | ) | × | 1 2 |
| = | 3 | × | 12 | − | 3 | × | 2 | x | − | x | ( | 12 | − | 2 | x | ) | × | 1 2 |
| = | 36 | − | 6 | x | − | x | ( | 12 | − | 2 | x | ) | × | 1 2 |
| = | 36 | − | 6 | x | − | x | × | 12 | × | 1 2 | + | x | × | 2 | x | × | 1 2 |
| = | 36 | − | 6 | x | − | x | × | 6 | + | x | × | 1 | x |
| = | 36 | − | 12 | x | + | x | × | 1 | x |
| 36 | − | 12 | x | + | x | × | 1 | x | = | 80 |