| ( | 100 | − | 55 | − | x | ) | ( | 50 | + | 4 | x | ) | = | 2800 |
| Left side of the equation = | 100 | ( | 50 | + | 4 | x | ) | − | 55 | ( | 50 | + | 4 | x | ) | − | x | ( | 50 | + | 4 | x | ) |
| = | 100 | × | 50 | + | 100 | × | 4 | x | − | 55 | ( | 50 | + | 4 | x | ) | − | x | ( | 50 | + | 4 | x | ) |
| = | 5000 | + | 400 | x | − | 55 | ( | 50 | + | 4 | x | ) | − | x | ( | 50 | + | 4 | x | ) |
| = | 5000 | + | 400 | x | − | 55 | × | 50 | − | 55 | × | 4 | x | − | x | ( | 50 | + | 4 | x | ) |
| = | 5000 | + | 400 | x | − | 2750 | − | 220 | x | − | x | ( | 50 | + | 4 | x | ) |
| = | 2250 | + | 180 | x | − | x | ( | 50 | + | 4 | x | ) |
| = | 2250 | + | 180 | x | − | x | × | 50 | − | x | × | 4 | x |
| = | 2250 | + | 130 | x | − | x | × | 4 | x |
| 2250 | + | 130 | x | − | x | × | 4 | x | = | 2800 |
| x2= | 55 2 |