| ( | 60 | − | x | ) | ( | 200 | + | 20 | x | ) | = | 24500 |
| Left side of the equation = | 60 | ( | 200 | + | 20 | x | ) | − | x | ( | 200 | + | 20 | x | ) |
| = | 60 | × | 200 | + | 60 | × | 20 | x | − | x | ( | 200 | + | 20 | x | ) |
| = | 12000 | + | 1200 | x | − | x | ( | 200 | + | 20 | x | ) |
| = | 12000 | + | 1200 | x | − | x | × | 200 | − | x | × | 20 | x |
| = | 12000 | + | 1000 | x | − | x | × | 20 | x |
| 12000 | + | 1000 | x | − | x | × | 20 | x | = | 24500 |