| ( | x | − | 30 | ) | ( | 1200 | − | 30 | ( | x | − | 30 | ) | ) | = | 36750 |
| Left side of the equation = | x | ( | 1200 | − | 30 | ( | x | − | 30 | ) | ) | − | 30 | ( | 1200 | − | 30 | ( | x | − | 30 | ) | ) |
| = | x | × | 1200 | − | x | × | 30 | ( | x | − | 30 | ) | − | 30 | ( | 1200 | − | 30 | ( | x | − | 30 | ) | ) |
| = | 1200 | x | − | x | × | 30 | x | + | x | × | 30 | × | 30 | − | 30 | ( | 1200 | − | 30 | ( | x | − | 30 | ) | ) |
| = | 1200 | x | − | x | × | 30 | x | + | x | × | 900 | − | 30 | ( | 1200 | − | 30 | ( | x | − | 30 | ) | ) |
| = | 2100 | x | − | x | × | 30 | x | − | 30 | ( | 1200 | − | 30 | ( | x | − | 30 | ) | ) |
| = | 2100 | x | − | x | × | 30 | x | − | 30 | × | 1200 | + | 30 | × | 30 | ( | x | − | 30 | ) |
| = | 2100 | x | − | x | × | 30 | x | − | 36000 | + | 900 | ( | x | − | 30 | ) |
| = | 2100 | x | − | x | × | 30 | x | − | 36000 | + | 900 | x | − | 900 | × | 30 |
| = | 2100 | x | − | x | × | 30 | x | − | 36000 | + | 900 | x | − | 27000 |
| = | 3000 | x | − | x | × | 30 | x | − | 63000 |
| 3000 | x | − | x | × | 30 | x | − | 63000 | = | 36750 |