| ( | 8 | − | a | ) | ( | 200 | + | 50 | a | ) | = | 1750 |
| Left side of the equation = | 8 | ( | 200 | + | 50 | a | ) | − | a | ( | 200 | + | 50 | a | ) |
| = | 8 | × | 200 | + | 8 | × | 50 | a | − | a | ( | 200 | + | 50 | a | ) |
| = | 1600 | + | 400 | a | − | a | ( | 200 | + | 50 | a | ) |
| = | 1600 | + | 400 | a | − | a | × | 200 | − | a | × | 50 | a |
| = | 1600 | + | 200 | a | − | a | × | 50 | a |
| 1600 | + | 200 | a | − | a | × | 50 | a | = | 1750 |