| ( | 100 | + | x | ) | ( | 1200 | − | 2 | x | ) | = | 24500 |
| Left side of the equation = | 100 | ( | 1200 | − | 2 | x | ) | + | x | ( | 1200 | − | 2 | x | ) |
| = | 100 | × | 1200 | − | 100 | × | 2 | x | + | x | ( | 1200 | − | 2 | x | ) |
| = | 120000 | − | 200 | x | + | x | ( | 1200 | − | 2 | x | ) |
| = | 120000 | − | 200 | x | + | x | × | 1200 | − | x | × | 2 | x |
| = | 120000 | + | 1000 | x | − | x | × | 2 | x |
| 120000 | + | 1000 | x | − | x | × | 2 | x | = | 24500 |