| ( | 10 | + | a | ) | ( | 500 | − | 2 | a | ) | = | 6000 |
| Left side of the equation = | 10 | ( | 500 | − | 2 | a | ) | + | a | ( | 500 | − | 2 | a | ) |
| = | 10 | × | 500 | − | 10 | × | 2 | a | + | a | ( | 500 | − | 2 | a | ) |
| = | 5000 | − | 20 | a | + | a | ( | 500 | − | 2 | a | ) |
| = | 5000 | − | 20 | a | + | a | × | 500 | − | a | × | 2 | a |
| = | 5000 | + | 480 | a | − | a | × | 2 | a |
| 5000 | + | 480 | a | − | a | × | 2 | a | = | 6000 |