| ( | 60 | − | 2 | x | ) | ( | 40 | − | 2 | x | ) | = | 1500 |
| Left side of the equation = | 60 | ( | 40 | − | 2 | x | ) | − | 2 | x | ( | 40 | − | 2 | x | ) |
| = | 60 | × | 40 | − | 60 | × | 2 | x | − | 2 | x | ( | 40 | − | 2 | x | ) |
| = | 2400 | − | 120 | x | − | 2 | x | ( | 40 | − | 2 | x | ) |
| = | 2400 | − | 120 | x | − | 2 | x | × | 40 | + | 2 | x | × | 2 | x |
| = | 2400 | − | 120 | x | − | 80 | x | + | 4 | x | x |
| = | 2400 | − | 200 | x | + | 4 | x | x |
| 2400 | − | 200 | x | + | 4 | x | x | = | 1500 |