( | 18 | − | X | ) | ( | 10 | X | + | 100 | ) | = | 1920 |
Left side of the equation = | 18 | ( | 10 | X | + | 100 | ) | − | X | ( | 10 | X | + | 100 | ) |
= | 18 | × | 10 | X | + | 18 | × | 100 | − | X | ( | 10 | X | + | 100 | ) |
= | 180 | X | + | 1800 | − | X | ( | 10 | X | + | 100 | ) |
= | 180 | X | + | 1800 | − | X | × | 10 | X | − | X | × | 100 |
= | 80 | X | + | 1800 | − | X | × | 10 | X |
80 | X | + | 1800 | − | X | × | 10 | X | = | 1920 |