| ( | 1 | + | a | ) | ( | 1500 | − | 50 | a | ) | = | 6500 |
| Left side of the equation = | 1 | ( | 1500 | − | 50 | a | ) | + | a | ( | 1500 | − | 50 | a | ) |
| = | 1 | × | 1500 | − | 1 | × | 50 | a | + | a | ( | 1500 | − | 50 | a | ) |
| = | 1500 | − | 50 | a | + | a | ( | 1500 | − | 50 | a | ) |
| = | 1500 | − | 50 | a | + | a | × | 1500 | − | a | × | 50 | a |
| = | 1500 | + | 1450 | a | − | a | × | 50 | a |
| 1500 | + | 1450 | a | − | a | × | 50 | a | = | 6500 |