| ( | 15 | − | 2 | x | ) | ( | 10 | − | x | ) | = | 88 |
| Left side of the equation = | 15 | ( | 10 | − | x | ) | − | 2 | x | ( | 10 | − | x | ) |
| = | 15 | × | 10 | − | 15 | x | − | 2 | x | ( | 10 | − | x | ) |
| = | 150 | − | 15 | x | − | 2 | x | ( | 10 | − | x | ) |
| = | 150 | − | 15 | x | − | 2 | x | × | 10 | + | 2 | x | x |
| = | 150 | − | 15 | x | − | 20 | x | + | 2 | x | x |
| = | 150 | − | 35 | x | + | 2 | x | x |
| 150 | − | 35 | x | + | 2 | x | x | = | 88 |
| x2= | 31 2 |