| 13 | × | 13 | − | x | x | = | 15 | × | 15 | − | ( | 14 | − | x | ) | ( | 14 | − | x | ) |
| Left side of the equation = | 169 | − | x | x |
| 169 | − | x | x | = | 15 | × | 15 | − | ( | 14 | − | x | ) | ( | 14 | − | x | ) |
| Right side of the equation = | 225 | − | ( | 14 | − | x | ) | ( | 14 | − | x | ) |
| 169 | − | x | x | = | 225 | − | ( | 14 | − | x | ) | ( | 14 | − | x | ) |
| Right side of the equation = | 225 | − | 14 | ( | 14 | − | x | ) | + | x | ( | 14 | − | x | ) |
| = | 225 | − | 14 | × | 14 | + | 14 | x | + | x | ( | 14 | − | x | ) |
| = | 225 | − | 196 | + | 14 | x | + | x | ( | 14 | − | x | ) |
| = | 29 | + | 14 | x | + | x | ( | 14 | − | x | ) |
| = | 29 | + | 14 | x | + | x | × | 14 | − | x | x |
| = | 29 | + | 28 | x | − | x | x |
| 169 | − | x | x | = | 29 | + | 28 | x | − | x | x |