| ( | x | − | 12 | ) | ( | 60 | + | 12 | ( | x | − | 20 | ) | ÷ | 2 | ) | = | 432 |
| Left side of the equation = | x | ( | 60 | + | 12 | ( | x | − | 20 | ) | ÷ | 2 | ) | − | 12 | ( | 60 | + | 12 | ( | x | − | 20 | ) | ÷ | 2 | ) |
| = | x | × | 60 | + | x | × | 12 | ( | x | − | 20 | ) | ÷ | 2 | − | 12 | ( | 60 | + | 12 | ( | x | − | 20 | ) | ÷ | 2 | ) |
| = | x | × | 60 | + | x | × | 6 | ( | x | − | 20 | ) | − | 12 | ( | 60 | + | 12 | ( | x | − | 20 | ) | ÷ | 2 | ) |
| = | 60 | x | + | x | × | 6 | x | − | x | × | 6 | × | 20 | − | 12 | ( | 60 | + | 12 | ( | x | − | 20 | ) | ÷ | 2 | ) |
| = | 60 | x | + | x | × | 6 | x | − | x | × | 120 | − | 12 | ( | 60 | + | 12 | ( | x | − | 20 | ) | ÷ | 2 | ) |
| = | - | 60 | x | + | x | × | 6 | x | − | 12 | ( | 60 | + | 12 | ( | x | − | 20 | ) | ÷ | 2 | ) |
| = | - | 60 | x | + | x | × | 6 | x | − | 12 | × | 60 | − | 12 | × | 12 | ( | x | − | 20 | ) | ÷ | 2 |
| = | - | 60 | x | + | x | × | 6 | x | − | 720 | − | 72 | ( | x | − | 20 | ) |
| = | - | 60 | x | + | x | × | 6 | x | − | 720 | − | 72 | x | + | 72 | × | 20 |
| = | - | 60 | x | + | x | × | 6 | x | − | 720 | − | 72 | x | + | 1440 |
| = | - | 132 | x | + | x | × | 6 | x | + | 720 |
| - | 132 | x | + | x | × | 6 | x | + | 720 | = | 432 |