( | 60 | − | x | ) | ( | 120 | + | 10 | x | ) | = | 1800 |
Left side of the equation = | 60 | ( | 120 | + | 10 | x | ) | − | x | ( | 120 | + | 10 | x | ) |
= | 60 | × | 120 | + | 60 | × | 10 | x | − | x | ( | 120 | + | 10 | x | ) |
= | 7200 | + | 600 | x | − | x | ( | 120 | + | 10 | x | ) |
= | 7200 | + | 600 | x | − | x | × | 120 | − | x | × | 10 | x |
= | 7200 | + | 480 | x | − | x | × | 10 | x |
7200 | + | 480 | x | − | x | × | 10 | x | = | 1800 |