| ( | 10 | − | x | ) | ( | 10 | − | x | ) | + | x | x | = | 68 |
| Left side of the equation = | 10 | ( | 10 | − | x | ) | − | x | ( | 10 | − | x | ) | + | x | x |
| = | 10 | × | 10 | − | 10 | x | − | x | ( | 10 | − | x | ) | + | x | x |
| = | 100 | − | 10 | x | − | x | ( | 10 | − | x | ) | + | x | x |
| = | 100 | − | 10 | x | − | x | × | 10 | + | x | x | + | x | x |
| = | 100 | − | 20 | x | + | x | x | + | x | x |
| 100 | − | 20 | x | + | x | x | + | x | x | = | 68 |