| ( | 16 | − | y | ) | ( | 480 | + | 40 | y | ) | = | 7680 |
| Left side of the equation = | 16 | ( | 480 | + | 40 | y | ) | − | y | ( | 480 | + | 40 | y | ) |
| = | 16 | × | 480 | + | 16 | × | 40 | y | − | y | ( | 480 | + | 40 | y | ) |
| = | 7680 | + | 640 | y | − | y | ( | 480 | + | 40 | y | ) |
| = | 7680 | + | 640 | y | − | y | × | 480 | − | y | × | 40 | y |
| = | 7680 | + | 160 | y | − | y | × | 40 | y |
| 7680 | + | 160 | y | − | y | × | 40 | y | = | 7680 |