We have to take the GCF (Greatest Common Factor) of 45 and 75 to get our answer.
We prime factorize the numbers. Shown below:
45 = 3 * 3 * 5
and
75 = 3 * 5 * 5
The greatest number of time 3 is common is 1 time
The greatest number o time 5 is common is 1 time
So,
GCF(45, 75) = 3 x 5 = 15 bags