| ( | 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 |