| ( | 15 | − | 10 | x | ) | ( | 10 | − | 8 | x | ) | = | 100 |
| Left side of the equation = | 15 | ( | 10 | − | 8 | x | ) | − | 10 | x | ( | 10 | − | 8 | x | ) |
| = | 15 | × | 10 | − | 15 | × | 8 | x | − | 10 | x | ( | 10 | − | 8 | x | ) |
| = | 150 | − | 120 | x | − | 10 | x | ( | 10 | − | 8 | x | ) |
| = | 150 | − | 120 | x | − | 10 | x | × | 10 | + | 10 | x | × | 8 | x |
| = | 150 | − | 120 | x | − | 100 | x | + | 80 | x | x |
| = | 150 | − | 220 | x | + | 80 | x | x |
| 150 | − | 220 | x | + | 80 | x | x | = | 100 |
| x1= | 1 4 |
| x2= | 5 2 |