| 800 | + | ( | 4 | − | x | ) | ( | 600 | − | 50 | x | ) | = | 1250 |
| Left side of the equation = | 800 | + | 4 | ( | 600 | − | 50 | x | ) | − | x | ( | 600 | − | 50 | x | ) |
| = | 800 | + | 4 | × | 600 | − | 4 | × | 50 | x | − | x | ( | 600 | − | 50 | x | ) |
| = | 800 | + | 2400 | − | 200 | x | − | x | ( | 600 | − | 50 | x | ) |
| = | 3200 | − | 200 | x | − | x | ( | 600 | − | 50 | x | ) |
| = | 3200 | − | 200 | x | − | x | × | 600 | + | x | × | 50 | x |
| = | 3200 | − | 800 | x | + | x | × | 50 | x |
| 3200 | − | 800 | x | + | x | × | 50 | x | = | 1250 |