| ( | 50 | − | n | ) | ( | 100 | + | 5 | n | ) | = | 0 |
| Left side of the equation = | 50 | ( | 100 | + | 5 | n | ) | − | n | ( | 100 | + | 5 | n | ) |
| = | 50 | × | 100 | + | 50 | × | 5 | n | − | n | ( | 100 | + | 5 | n | ) |
| = | 5000 | + | 250 | n | − | n | ( | 100 | + | 5 | n | ) |
| = | 5000 | + | 250 | n | − | n | × | 100 | − | n | × | 5 | n |
| = | 5000 | + | 150 | n | − | n | × | 5 | n |
| 5000 | + | 150 | n | − | n | × | 5 | n | = | 0 |