| ( | 5600 | − | 1800 | ) | × | 20 100 | − | ( | 6000 | × | 8 100 | − | x | ) | = | 504 |
| Left side of the equation = | 5600 | × | 20 100 | − | 1800 | × | 20 100 | − | ( | 6000 | × | 8 100 | − | x | ) |
| = | 1120 | − | 360 | − | ( | 6000 | × | 8 100 | − | x | ) |
| = | 760 | − | ( | 6000 | × | 8 100 | − | x | ) |
| = | 760 | − | 6000 | × | 8 100 | + | x |
| = | 760 | − | 480 | + | x |
| = | 280 | + | x |
| 280 | + | x | = | 504 |
| x | = | 504 | − | 280 |
| x | = | 224 |