| ( | x | − | 2500 | ) | ( | 12000 | − | 4 | x | ) | = | 100 |
| Left side of the equation = | x | ( | 12000 | − | 4 | x | ) | − | 2500 | ( | 12000 | − | 4 | x | ) |
| = | x | × | 12000 | − | x | × | 4 | x | − | 2500 | ( | 12000 | − | 4 | x | ) |
| = | 12000 | x | − | x | × | 4 | x | − | 2500 | × | 12000 | + | 2500 | × | 4 | x |
| = | 12000 | x | − | x | × | 4 | x | − | 30000000 | + | 10000 | x |
| = | 22000 | x | − | x | × | 4 | x | − | 30000000 |
| 22000 | x | − | x | × | 4 | x | − | 30000000 | = | 100 |