| x | ( | 30 | − | 2 | x | ) | ( | 20 | − | 2 | x | ) | = | 264 |
| Left side of the equation = | x | × | 30 | ( | 20 | − | 2 | x | ) | − | x | × | 2 | x | ( | 20 | − | 2 | x | ) |
| = | x | × | 30 | × | 20 | − | x | × | 30 | × | 2 | x | − | x | × | 2 | x | ( | 20 | − | 2 | x | ) |
| = | x | × | 600 | − | x | × | 60 | x | − | x | × | 2 | x | ( | 20 | − | 2 | x | ) |
| = | 600 | x | − | x | × | 60 | x | − | x | × | 2 | x | × | 20 | + | x | × | 2 | x |
| = | 600 | x | − | x | × | 60 | x | − | x | × | 40 | x | + | x | × | 4 | x | x |
| 600 | x | − | x | × | 60 | x | − | x | × | 40 | x | + | x | × | 4 | x | x | = | 264 |