| ( | 16 | + | x | ) | ( | 480 | − | 20 | x | ) | = | 7680 |
| Left side of the equation = | 16 | ( | 480 | − | 20 | x | ) | + | x | ( | 480 | − | 20 | x | ) |
| = | 16 | × | 480 | − | 16 | × | 20 | x | + | x | ( | 480 | − | 20 | x | ) |
| = | 7680 | − | 320 | x | + | x | ( | 480 | − | 20 | x | ) |
| = | 7680 | − | 320 | x | + | x | × | 480 | − | x | × | 20 | x |
| = | 7680 | + | 160 | x | − | x | × | 20 | x |
| 7680 | + | 160 | x | − | x | × | 20 | x | = | 7680 |