Answer:
The GCF (Greatest Common Factor) is the biggest factor common to both of these numbers, so we must determine the factors for each:
15--->1,15
3,5
20--->1,20
2,10
4,5
As we can see, 1 and 5 are the common factors and 5 is the biggest (greatest). Therefore, we can "pull" out a 5 from both numbers and get a resulting equation of:
15 + 20--->5(3 + 4)
Hope this helps!
Explanation: