| 1440 | = | ( | x | − | 6 | ) | ( | 600 | − | 30 | x | ) |
| Right side of the equation = | x | ( | 600 | − | 30 | x | ) | − | 6 | ( | 600 | − | 30 | x | ) |
| = | x | × | 600 | − | x | × | 30 | x | − | 6 | ( | 600 | − | 30 | x | ) |
| = | 600 | x | − | x | × | 30 | x | − | 6 | × | 600 | + | 6 | × | 30 | x |
| = | 600 | x | − | x | × | 30 | x | − | 3600 | + | 180 | x |
| = | 780 | x | − | x | × | 30 | x | − | 3600 |
| 1440 | = | 780 | x | − | x | × | 30 | x | − | 3600 |