| ( | - | 20 | x | + | 2600 | ) | ( | x | − | 50 | ) | = | 24000 |
| Left side of the equation = | - | 20 | x | ( | x | − | 50 | ) | + | 2600 | ( | x | − | 50 | ) |
| = | - | 20 | x | x | + | 20 | x | × | 50 | + | 2600 | ( | x | − | 50 | ) |
| = | - | 20 | x | x | + | 1000 | x | + | 2600 | ( | x | − | 50 | ) |
| = | - | 20 | x | x | + | 1000 | x | + | 2600 | x | − | 2600 | × | 50 |
| = | - | 20 | x | x | + | 1000 | x | + | 2600 | x | − | 130000 |
| = | - | 20 | x | x | + | 3600 | x | − | 130000 |
| - | 20 | x | x | + | 3600 | x | − | 130000 | = | 24000 |