| ( | 30 | − | X | ) | X | ( | 20 | − | 2 | X | ) | = | 448 |
| Left side of the equation = | 30 | X | ( | 20 | − | 2 | X | ) | − | X | X | ( | 20 | − | 2 | X | ) |
| = | 30 | X | × | 20 | − | 30 | X | × | 2 | X | − | X | X | ( | 20 | − | 2 | X | ) |
| = | 600 | X | − | 60 | X | X | − | X | X | ( | 20 | − | 2 | X | ) |
| = | 600 | X | − | 60 | X | X | − | X | X | × | 20 | + | X | X | × | 2 | X |
| 600 | X | − | 60 | X | X | − | X | X | × | 20 | + | X | X | × | 2 | X | = | 448 |