| ( | 7 10 | x | − | 1 20 | x | ) | ( | 5000 | + | 1000 | x | ) | = | 4500 |
| Left side of the equation = | 7 10 | x | ( | 5000 | + | 1000 | x | ) | − | 1 20 | x | ( | 5000 | + | 1000 | x | ) |
| = | 7 10 | x | × | 5000 | + | 7 10 | x | × | 1000 | x | − | 1 20 | x | ( | 5000 | + | 1000 | x | ) |
| = | 3500 | x | + | 700 | x | x | − | 1 20 | x | ( | 5000 | + | 1000 | x | ) |
| = | 3500 | x | + | 700 | x | x | − | 1 20 | x | × | 5000 | − | 1 20 | x | × | 1000 | x |
| = | 3500 | x | + | 700 | x | x | − | 250 | x | − | 50 | x | x |
| = | 3250 | x | + | 700 | x | x | − | 50 | x | x |
| 3250 | x | + | 700 | x | x | − | 50 | x | x | = | 4500 |