| 78 | + | 88 | = | ( | 78 | + | x | ) | ( | 88 | − | x | ) |
| Left side of the equation = | 166 |
| 166 | = | ( | 78 | + | x | ) | ( | 88 | − | x | ) |
| Right side of the equation = | 78 | ( | 88 | − | x | ) | + | x | ( | 88 | − | x | ) |
| = | 78 | × | 88 | − | 78 | x | + | x | ( | 88 | − | x | ) |
| = | 6864 | − | 78 | x | + | x | ( | 88 | − | x | ) |
| = | 6864 | − | 78 | x | + | x | × | 88 | − | x | x |
| = | 6864 | + | 10 | x | − | x | x |
| 166 | = | 6864 | + | 10 | x | − | x | x |