| ( | 44 | − | x | ) | ( | 20 | − | 5 | x | x | ) | = | 1990 |
| Left side of the equation = | 44 | ( | 20 | − | 5 | x | x | ) | − | x | ( | 20 | − | 5 | x | x | ) |
| = | 44 | × | 20 | − | 44 | × | 5 | x | x | − | x | ( | 20 | − | 5 | x | x | ) |
| = | 880 | − | 220 | x | x | − | x | ( | 20 | − | 5 | x | x | ) |
| = | 880 | − | 220 | x | x | − | x | × | 20 | + | x | × | 5 | x | x |
| 880 | − | 220 | x | x | − | 20 | x | + | x | × | 5 | x | x | = | 1990 |