LCM: 54
GCD: 6
GCM(18, 42) = 6
If GCM stands for Greatest Common Multiple, there is no such number. This is because if x is claimed as the GCM then 2x is a common multiple of both 6 and 8 and 2x > x.
12
2.
The answer is 6
The LCM is 270. The GCM is infinite.
The LCF is 1. The GCF is 18. The LCM is 108. The GCM is infinite.
192.
The greatest common multiple is infinite.
The GCM is infinite.
9
There can be no GCM (Greatest Common Multiple). Suppose a GCM exists and suppose it is x. That is, x is the GCM of 7 and 13, then 2x is a multiple of both 7 and 13 and is greater than x. This contradicts the statement that x is the GCM. So x cannot be the GCM.