| ( | 5 | + | x | ) | ( | 300 | − | 10 | x | ) | = | 2500 |
| Left side of the equation = | 5 | ( | 300 | − | 10 | x | ) | + | x | ( | 300 | − | 10 | x | ) |
| = | 5 | × | 300 | − | 5 | × | 10 | x | + | x | ( | 300 | − | 10 | x | ) |
| = | 1500 | − | 50 | x | + | x | ( | 300 | − | 10 | x | ) |
| = | 1500 | − | 50 | x | + | x | × | 300 | − | x | × | 10 | x |
| = | 1500 | + | 250 | x | − | x | × | 10 | x |
| 1500 | + | 250 | x | − | x | × | 10 | x | = | 2500 |