| ( | 92 | − | 2 | a | ) | ( | 60 | − | a | ) | = | 885 |
| Left side of the equation = | 92 | ( | 60 | − | a | ) | − | 2 | a | ( | 60 | − | a | ) |
| = | 92 | × | 60 | − | 92 | a | − | 2 | a | ( | 60 | − | a | ) |
| = | 5520 | − | 92 | a | − | 2 | a | ( | 60 | − | a | ) |
| = | 5520 | − | 92 | a | − | 2 | a | × | 60 | + | 2 | a | a |
| = | 5520 | − | 92 | a | − | 120 | a | + | 2 | a | a |
| = | 5520 | − | 212 | a | + | 2 | a | a |
| 5520 | − | 212 | a | + | 2 | a | a | = | 885 |