| ( | 300 | − | 10 | x | ) | ( | 40 | − | x | ) | − | ( | 800 | − | 20 | x | + | 5 | x | ) | = | 11350 |
| Left side of the equation = | 300 | ( | 40 | − | x | ) | − | 10 | x | ( | 40 | − | x | ) | − | ( | 800 | − | 20 | x | + | 5 | x | ) |
| = | 300 | × | 40 | − | 300 | x | − | 10 | x | ( | 40 | − | x | ) | − | ( | 800 | − | 20 | x | + | 5 | x | ) |
| = | 12000 | − | 300 | x | − | 10 | x | ( | 40 | − | x | ) | − | ( | 800 | − | 20 | x | + | 5 | x | ) |
| = | 12000 | − | 300 | x | − | 10 | x | × | 40 | + | 10 | x | x | − | ( | 800 | − | 20 | x | + | 5 | x | ) |
| = | 12000 | − | 300 | x | − | 400 | x | + | 10 | x | x | − | ( | 800 | − | 20 | x | + | 5 | x | ) |
| = | 12000 | − | 700 | x | + | 10 | x | x | − | ( | 800 | − | 20 | x | + | 5 | x | ) |
| = | 12000 | − | 700 | x | + | 10 | x | x | − | 800 | + | 20 | x | − | 5 | x |
| = | 11200 | − | 685 | x | + | 10 | x | x |
| 11200 | − | 685 | x | + | 10 | x | x | = | 11350 |