| ( | 4 | − | x | ) | ( | 20 | + | 4 | x | ) | − | 10 | = | 62 |
| Left side of the equation = | 4 | ( | 20 | + | 4 | x | ) | − | x | ( | 20 | + | 4 | x | ) | − | 10 |
| = | 4 | × | 20 | + | 4 | × | 4 | x | − | x | ( | 20 | + | 4 | x | ) | − | 10 |
| = | 80 | + | 16 | x | − | x | ( | 20 | + | 4 | x | ) | − | 10 |
| = | 70 | + | 16 | x | − | x | ( | 20 | + | 4 | x | ) |
| = | 70 | + | 16 | x | − | x | × | 20 | − | x | × | 4 | x |
| = | 70 | − | 4 | x | − | x | × | 4 | x |
| 70 | − | 4 | x | − | x | × | 4 | x | = | 62 |