| ( | x | − | 20 | ) | ( | 300 | − | 5 | x | ) | = | 2625 |
| Left side of the equation = | x | ( | 300 | − | 5 | x | ) | − | 20 | ( | 300 | − | 5 | x | ) |
| = | x | × | 300 | − | x | × | 5 | x | − | 20 | ( | 300 | − | 5 | x | ) |
| = | 300 | x | − | x | × | 5 | x | − | 20 | × | 300 | + | 20 | × | 5 | x |
| = | 300 | x | − | x | × | 5 | x | − | 6000 | + | 100 | x |
| = | 400 | x | − | x | × | 5 | x | − | 6000 |
| 400 | x | − | x | × | 5 | x | − | 6000 | = | 2625 |