Answer:
5
Explanation:
GCF is the greatest common factor; it's basically the biggest number that can divide the two numbers given. Here, our two numbers are 15 and 10945. In order to figure out their GCF, we need to find each of these two numbers' prime factorization. Prime factorization is when we break up numbers into the product of their prime factors.
15 = 3 * 5 (3 and 5 are both prime numbers)
10945 = 5 * 11 * 199 (5, 11, and 199 are all prime numbers)
Just looking at these prime factorizations, we can tell that the only, and biggest, number they share is 5.
So, 5 is the GCF.
Hope this helps!