| ( | 15 | − | a | ) | ( | 4 | a | + | 256 | ) | = | 4200 |
| Left side of the equation = | 15 | ( | 4 | a | + | 256 | ) | − | a | ( | 4 | a | + | 256 | ) |
| = | 15 | × | 4 | a | + | 15 | × | 256 | − | a | ( | 4 | a | + | 256 | ) |
| = | 60 | a | + | 3840 | − | a | ( | 4 | a | + | 256 | ) |
| = | 60 | a | + | 3840 | − | a | × | 4 | a | − | a | × | 256 |
| = | - | 196 | a | + | 3840 | − | a | × | 4 | a |
| - | 196 | a | + | 3840 | − | a | × | 4 | a | = | 4200 |