| ( | 37 | − | x | − | 25 | ) | ( | 2 | + | x | ) | = | 90 |
| Left side of the equation = | 37 | ( | 2 | + | x | ) | − | x | ( | 2 | + | x | ) | − | 25 | ( | 2 | + | x | ) |
| = | 37 | × | 2 | + | 37 | x | − | x | ( | 2 | + | x | ) | − | 25 | ( | 2 | + | x | ) |
| = | 74 | + | 37 | x | − | x | ( | 2 | + | x | ) | − | 25 | ( | 2 | + | x | ) |
| = | 74 | + | 37 | x | − | x | × | 2 | − | x | x | − | 25 | ( | 2 | + | x | ) |
| = | 74 | + | 35 | x | − | x | x | − | 25 | ( | 2 | + | x | ) |
| = | 74 | + | 35 | x | − | x | x | − | 25 | × | 2 | − | 25 | x |
| = | 74 | + | 35 | x | − | x | x | − | 50 | − | 25 | x |
| = | 24 | + | 10 | x | − | x | x |
| 24 | + | 10 | x | − | x | x | = | 90 |