| ( | 20 | + | x | ) | ( | 60 | − | 2 | x | ) | − | 10 | ( | 60 | − | 2 | x | ) | = | 600 |
| Left side of the equation = | 20 | ( | 60 | − | 2 | x | ) | + | x | ( | 60 | − | 2 | x | ) | − | 10 | ( | 60 | − | 2 | x | ) |
| = | 20 | × | 60 | − | 20 | × | 2 | x | + | x | ( | 60 | − | 2 | x | ) | − | 10 | ( | 60 | − | 2 | x | ) |
| = | 1200 | − | 40 | x | + | x | ( | 60 | − | 2 | x | ) | − | 10 | ( | 60 | − | 2 | x | ) |
| = | 1200 | − | 40 | x | + | x | × | 60 | − | x | × | 2 | x | − | 10 | ( | 60 | − | 2 | x | ) |
| = | 1200 | + | 20 | x | − | x | × | 2 | x | − | 10 | ( | 60 | − | 2 | x | ) |
| = | 1200 | + | 20 | x | − | x | × | 2 | x | − | 10 | × | 60 | + | 10 | × | 2 | x |
| = | 1200 | + | 20 | x | − | x | × | 2 | x | − | 600 | + | 20 | x |
| = | 600 | + | 40 | x | − | x | × | 2 | x |
| 600 | + | 40 | x | − | x | × | 2 | x | = | 600 |