| ( | 50 | + | x | ) | ( | 600 | − | 5 | x | ) | = | 0 |
| Left side of the equation = | 50 | ( | 600 | − | 5 | x | ) | + | x | ( | 600 | − | 5 | x | ) |
| = | 50 | × | 600 | − | 50 | × | 5 | x | + | x | ( | 600 | − | 5 | x | ) |
| = | 30000 | − | 250 | x | + | x | ( | 600 | − | 5 | x | ) |
| = | 30000 | − | 250 | x | + | x | × | 600 | − | x | × | 5 | x |
| = | 30000 | + | 350 | x | − | x | × | 5 | x |
| 30000 | + | 350 | x | − | x | × | 5 | x | = | 0 |