4 5 | ( | 800 | − | 2 | x | ) | ( | 600 | − | 10 | x | ) | = | 480000 |
| Left side of the equation = | 4 5 | × | 800 | ( | 600 | − | 10 | x | ) | − | 4 5 | × | 2 | x | ( | 600 | − | 10 | x | ) |
| = | 640 | ( | 600 | − | 10 | x | ) | − | 8 5 | x | ( | 600 | − | 10 | x | ) |
| = | 640 | × | 600 | − | 640 | × | 10 | x | − | 8 5 | x | ( | 600 | − | 10 | x | ) |
| = | 384000 | − | 6400 | x | − | 8 5 | x | ( | 600 | − | 10 | x | ) |
| = | 384000 | − | 6400 | x | − | 8 5 | x | × | 600 | + | 8 5 | x | × | 10 | x |
| = | 384000 | − | 6400 | x | − | 960 | x | + | 16 | x | x |
| = | 384000 | − | 7360 | x | + | 16 | x | x |
| 384000 | − | 7360 | x | + | 16 | x | x | = | 480000 |