| ( | 50 | − | x | ) | ( | 30 | − | x | ) | = | 30 | × | 50 | × | 1 4 |
| Left side of the equation = | 50 | ( | 30 | − | x | ) | − | x | ( | 30 | − | x | ) |
| = | 50 | × | 30 | − | 50 | x | − | x | ( | 30 | − | x | ) |
| = | 1500 | − | 50 | x | − | x | ( | 30 | − | x | ) |
| = | 1500 | − | 50 | x | − | x | × | 30 | + | x | x |
| = | 1500 | − | 80 | x | + | x | x |
| 1500 | − | 80 | x | + | x | x | = | 30 | × | 50 | × | 1 4 |
| Right side of the equation = | 375 |
| 1500 | − | 80 | x | + | x | x | = | 375 |