| ( | 50 | − | x | ) | ( | 20 | + | 4 | x | ) | − | 50 | = | 2750 |
| Left side of the equation = | 50 | ( | 20 | + | 4 | x | ) | − | x | ( | 20 | + | 4 | x | ) | − | 50 |
| = | 50 | × | 20 | + | 50 | × | 4 | x | − | x | ( | 20 | + | 4 | x | ) | − | 50 |
| = | 1000 | + | 200 | x | − | x | ( | 20 | + | 4 | x | ) | − | 50 |
| = | 950 | + | 200 | x | − | x | ( | 20 | + | 4 | x | ) |
| = | 950 | + | 200 | x | − | x | × | 20 | − | x | × | 4 | x |
| = | 950 | + | 180 | x | − | x | × | 4 | x |
| 950 | + | 180 | x | − | x | × | 4 | x | = | 2750 |