| ( | 60 | − | 5 | x | ) | ( | 4 | + | x | ) | = | 300 |
| Left side of the equation = | 60 | ( | 4 | + | x | ) | − | 5 | x | ( | 4 | + | x | ) |
| = | 60 | × | 4 | + | 60 | x | − | 5 | x | ( | 4 | + | x | ) |
| = | 240 | + | 60 | x | − | 5 | x | ( | 4 | + | x | ) |
| = | 240 | + | 60 | x | − | 5 | x | × | 4 | − | 5 | x | x |
| = | 240 | + | 60 | x | − | 20 | x | − | 5 | x | x |
| = | 240 | + | 40 | x | − | 5 | x | x |
| 240 | + | 40 | x | − | 5 | x | x | = | 300 |