You cannot find the LCM of one number. There must be two numbers to compare, because the C means common.
The LCM is: 72
126
90
Since 36 is a multiple of 18, it is automatically the LCM.
The LCM of the given three numbers is 198
Least Common Multiple (LCM) for 18 20 is 180
The LCM is: 36
3 and 18 6 and 9
4.2
NO
It is: 18
2