| ( | 2 | − | x | ) | ( | 20 | + | 40 | x | ) | = | 60 |
| Left side of the equation = | 2 | ( | 20 | + | 40 | x | ) | − | x | ( | 20 | + | 40 | x | ) |
| = | 2 | × | 20 | + | 2 | × | 40 | x | − | x | ( | 20 | + | 40 | x | ) |
| = | 40 | + | 80 | x | − | x | ( | 20 | + | 40 | x | ) |
| = | 40 | + | 80 | x | − | x | × | 20 | − | x | × | 40 | x |
| = | 40 | + | 60 | x | − | x | × | 40 | x |
| 40 | + | 60 | x | − | x | × | 40 | x | = | 60 |
| x1= | 1 2 |
| x2=1 |