| ( | 100 | + | 4 | x | ) | ( | 35 | − | x | ) | = | 3600 |
| Left side of the equation = | 100 | ( | 35 | − | x | ) | + | 4 | x | ( | 35 | − | x | ) |
| = | 100 | × | 35 | − | 100 | x | + | 4 | x | ( | 35 | − | x | ) |
| = | 3500 | − | 100 | x | + | 4 | x | ( | 35 | − | x | ) |
| = | 3500 | − | 100 | x | + | 4 | x | × | 35 | − | 4 | x | x |
| = | 3500 | − | 100 | x | + | 140 | x | − | 4 | x | x |
| = | 3500 | + | 40 | x | − | 4 | x | x |
| 3500 | + | 40 | x | − | 4 | x | x | = | 3600 |