| ( | 20 | + | 2 | X | ) | ( | 40 | − | X | ) | = | 1500 |
| Left side of the equation = | 20 | ( | 40 | − | X | ) | + | 2 | X | ( | 40 | − | X | ) |
| = | 20 | × | 40 | − | 20 | X | + | 2 | X | ( | 40 | − | X | ) |
| = | 800 | − | 20 | X | + | 2 | X | ( | 40 | − | X | ) |
| = | 800 | − | 20 | X | + | 2 | X | × | 40 | − | 2 | X | X |
| = | 800 | − | 20 | X | + | 80 | X | − | 2 | X | X |
| = | 800 | + | 60 | X | − | 2 | X | X |
| 800 | + | 60 | X | − | 2 | X | X | = | 1500 |