| ( | 30 | − | 3 2 | x | ) | ( | 31 | − | 2 | x | ) | = | 789 100 |
| Left side of the equation = | 30 | ( | 31 | − | 2 | x | ) | − | 3 2 | x | ( | 31 | − | 2 | x | ) |
| = | 30 | × | 31 | − | 30 | × | 2 | x | − | 3 2 | x | ( | 31 | − | 2 | x | ) |
| = | 930 | − | 60 | x | − | 3 2 | x | ( | 31 | − | 2 | x | ) |
| = | 930 | − | 60 | x | − | 3 2 | x | × | 31 | + | 3 2 | x | × | 2 | x |
| = | 930 | − | 60 | x | − | 93 2 | x | + | 3 | x | x |
| = | 930 | − | 213 2 | x | + | 3 | x | x |
| 930 | − | 213 2 | x | + | 3 | x | x | = | 789 100 |