| ( | 8 | + | x | ) | ( | 800 | − | 25 | x | ) | = | 10000 |
| Left side of the equation = | 8 | ( | 800 | − | 25 | x | ) | + | x | ( | 800 | − | 25 | x | ) |
| = | 8 | × | 800 | − | 8 | × | 25 | x | + | x | ( | 800 | − | 25 | x | ) |
| = | 6400 | − | 200 | x | + | x | ( | 800 | − | 25 | x | ) |
| = | 6400 | − | 200 | x | + | x | × | 800 | − | x | × | 25 | x |
| = | 6400 | + | 600 | x | − | x | × | 25 | x |
| 6400 | + | 600 | x | − | x | × | 25 | x | = | 10000 |