( | 20 | − | a | ) | ( | 720 | + | 6 | a | ) | = | 11250 |
Left side of the equation = | 20 | ( | 720 | + | 6 | a | ) | − | a | ( | 720 | + | 6 | a | ) |
= | 20 | × | 720 | + | 20 | × | 6 | a | − | a | ( | 720 | + | 6 | a | ) |
= | 14400 | + | 120 | a | − | a | ( | 720 | + | 6 | a | ) |
= | 14400 | + | 120 | a | − | a | × | 720 | − | a | × | 6 | a |
= | 14400 | − | 600 | a | − | a | × | 6 | a |
14400 | − | 600 | a | − | a | × | 6 | a | = | 11250 |