| ( | ( | 30 | − | x | ) | − | 15 | ) | ( | 200 | + | 50 | x | ) | = | 3500 |
| Left side of the equation = | ( | 30 | − | x | ) | ( | 200 | + | 50 | x | ) | − | 15 | ( | 200 | + | 50 | x | ) |
| = | 30 | ( | 200 | + | 50 | x | ) | − | x | ( | 200 | + | 50 | x | ) | − | 15 | ( | 200 | + | 50 | x | ) |
| = | 30 | × | 200 | + | 30 | × | 50 | x | − | x | ( | 200 | + | 50 | x | ) | − | 15 | ( | 200 | + | 50 | x | ) |
| = | 6000 | + | 1500 | x | − | x | ( | 200 | + | 50 | x | ) | − | 15 | ( | 200 | + | 50 | x | ) |
| = | 6000 | + | 1500 | x | − | x | × | 200 | − | x | × | 50 | x | − | 15 | ( | 200 | + | 50 | x | ) |
| = | 6000 | + | 1300 | x | − | x | × | 50 | x | − | 15 | ( | 200 | + | 50 | x | ) |
| = | 6000 | + | 1300 | x | − | x | × | 50 | x | − | 15 | × | 200 | − | 15 | × | 50 | x |
| = | 6000 | + | 1300 | x | − | x | × | 50 | x | − | 3000 | − | 750 | x |
| = | 3000 | + | 550 | x | − | x | × | 50 | x |
| 3000 | + | 550 | x | − | x | × | 50 | x | = | 3500 |