27 25 | = | ( | 1 10 | − | x | ) | ( | 1 20 | − | x | ) |
| Right side of the equation = | 1 10 | ( | 1 20 | − | x | ) | − | x | ( | 1 20 | − | x | ) |
| = | 1 10 | × | 1 20 | − | 1 10 | x | − | x | ( | 1 20 | − | x | ) |
| = | 1 200 | − | 1 10 | x | − | x | ( | 1 20 | − | x | ) |
| = | 1 200 | − | 1 10 | x | − | x | × | 1 20 | + | x | x |
| = | 1 200 | − | 3 20 | x | + | x | x |
27 25 | = | 1 200 | − | 3 20 | x | + | x | x |