| ( | 37 | − | 25 | − | x | ) | ( | 4 | + | 2 | x | ) | = | 90 |
| Left side of the equation = | 37 | ( | 4 | + | 2 | x | ) | − | 25 | ( | 4 | + | 2 | x | ) | − | x | ( | 4 | + | 2 | x | ) |
| = | 37 | × | 4 | + | 37 | × | 2 | x | − | 25 | ( | 4 | + | 2 | x | ) | − | x | ( | 4 | + | 2 | x | ) |
| = | 148 | + | 74 | x | − | 25 | ( | 4 | + | 2 | x | ) | − | x | ( | 4 | + | 2 | x | ) |
| = | 148 | + | 74 | x | − | 25 | × | 4 | − | 25 | × | 2 | x | − | x | ( | 4 | + | 2 | x | ) |
| = | 148 | + | 74 | x | − | 100 | − | 50 | x | − | x | ( | 4 | + | 2 | x | ) |
| = | 48 | + | 24 | x | − | x | ( | 4 | + | 2 | x | ) |
| = | 48 | + | 24 | x | − | x | × | 4 | − | x | × | 2 | x |
| = | 48 | + | 20 | x | − | x | × | 2 | x |
| 48 | + | 20 | x | − | x | × | 2 | x | = | 90 |