| ( | x | + | 5 | ) | ( | 700 | − | 20 | x | ) | = | 0 |
| Left side of the equation = | x | ( | 700 | − | 20 | x | ) | + | 5 | ( | 700 | − | 20 | x | ) |
| = | x | × | 700 | − | x | × | 20 | x | + | 5 | ( | 700 | − | 20 | x | ) |
| = | 700 | x | − | x | × | 20 | x | + | 5 | × | 700 | − | 5 | × | 20 | x |
| = | 700 | x | − | x | × | 20 | x | + | 3500 | − | 100 | x |
| = | 600 | x | − | x | × | 20 | x | + | 3500 |
| 600 | x | − | x | × | 20 | x | + | 3500 | = | 0 |