| ( | X | − | 100 | ) | ( | 300 | + | 5 | X | ) | = | 3200 |
| Left side of the equation = | X | ( | 300 | + | 5 | X | ) | − | 100 | ( | 300 | + | 5 | X | ) |
| = | X | × | 300 | + | X | × | 5 | X | − | 100 | ( | 300 | + | 5 | X | ) |
| = | 300 | X | + | X | × | 5 | X | − | 100 | × | 300 | − | 100 | × | 5 | X |
| = | 300 | X | + | X | × | 5 | X | − | 30000 | − | 500 | X |
| = | - | 200 | X | + | X | × | 5 | X | − | 30000 |
| - | 200 | X | + | X | × | 5 | X | − | 30000 | = | 3200 |