| ( | x | − | 60 | ) | ( | 1800 | − | 10 | x | ) | = | 0 |
| Left side of the equation = | x | ( | 1800 | − | 10 | x | ) | − | 60 | ( | 1800 | − | 10 | x | ) |
| = | x | × | 1800 | − | x | × | 10 | x | − | 60 | ( | 1800 | − | 10 | x | ) |
| = | 1800 | x | − | x | × | 10 | x | − | 60 | × | 1800 | + | 60 | × | 10 | x |
| = | 1800 | x | − | x | × | 10 | x | − | 108000 | + | 600 | x |
| = | 2400 | x | − | x | × | 10 | x | − | 108000 |
| 2400 | x | − | x | × | 10 | x | − | 108000 | = | 0 |