| ( | X | − | 2 | ) | ( | X | − | 2 | ) | + | ( | 3 | X | − | 6 | ) | ( | 3 | X | − | 6 | ) | = | 20 |
| Left side of the equation = | X | ( | X | − | 2 | ) | − | 2 | ( | X | − | 2 | ) | + | ( | 3 | X | − | 6 | ) | ( | 3 | X | − | 6 | ) |
| = | X | X | − | X | × | 2 | − | 2 | ( | X | − | 2 | ) | + | ( | 3 | X | − | 6 | ) | ( | 3 | X | − | 6 | ) |
| = | X | X | − | 2 | X | − | 2 | X | + | 2 | × | 2 | + | ( | 3 | X | − | 6 | ) | ( | 3 | X | − | 6 | ) |
| = | X | X | − | 2 | X | − | 2 | X | + | 4 | + | ( | 3 | X | − | 6 | ) | ( | 3 | X | − | 6 | ) |
| = | X | X | − | 4 | X | + | 4 | + | ( | 3 | X | − | 6 | ) | ( | 3 | X | − | 6 | ) |
| = | X | X | − | 4 | X | + | 4 | + | 3 | X | ( | 3 | X | − | 6 | ) | − | 6 | ( | 3 | X | − | 6 | ) |
| = | X | X | − | 4 | X | + | 4 | + | 3 | X | × | 3 | X | − | 3 | X | × | 6 |
| = | X | X | − | 4 | X | + | 4 | + | 9 | X | X | − | 18 | X | − | 6 | ( | 3 | X | − | 6 | ) |
| = | X | X | − | 22 | X | + | 4 | + | 9 | X | X | − | 6 | ( | 3 | X | − | 6 | ) |
| = | X | X | − | 22 | X | + | 4 | + | 9 | X | X | − | 6 | × | 3 | X | + | 6 |
| = | X | X | − | 22 | X | + | 4 | + | 9 | X | X | − | 18 | X | + | 36 |
| = | X | X | − | 40 | X | + | 40 | + | 9 | X | X |
| X | X | − | 40 | X | + | 40 | + | 9 | X | X | = | 20 |