Answer: 6m
Explanation:
GCF is Greatest Common Factor.
In other words, what is the biggest factor they have in common?
You can factor both terms down to their primes and compare them:
24m 18m
∧ ∧
4 6 m 2 9 m
∧ ∧ ↓ ↓ ∧ ↓
2 2 2 3 m 2 3 3 m
24m: 2 · 2 · 2 · 3 · m
18m: 2 · 3 · 3 · m
What do they have in common?
24m: 2 · 2 · 2 · 3 · m Common is 6m, leftover is 4
18m: 2 · 3 · 3 · m Common is 6m, leftover is 3
I showed the leftover because you need that to find the LCM