| ( | 80 | − | 2 | x | ) | ( | x | − | 15 | ) | = | 200 |
| Left side of the equation = | 80 | ( | x | − | 15 | ) | − | 2 | x | ( | x | − | 15 | ) |
| = | 80 | x | − | 80 | × | 15 | − | 2 | x | ( | x | − | 15 | ) |
| = | 80 | x | − | 1200 | − | 2 | x | ( | x | − | 15 | ) |
| = | 80 | x | − | 1200 | − | 2 | x | x | + | 2 | x | × | 15 |
| = | 80 | x | − | 1200 | − | 2 | x | x | + | 30 | x |
| = | 110 | x | − | 1200 | − | 2 | x | x |
| 110 | x | − | 1200 | − | 2 | x | x | = | 200 |