Answer:
The GCF is going to be 7
Step-by-step explanation:
This Is how I find the GCF of 2 numbers. I find the prime factorization first, then I find the common factors and multiply them. Here
The prime factorization of 21, 3 × 7 = 21
The prime factorization of 28, 2 × 2 × 7 = 28
The one and THE only common factor is 7, which is going to be the GCF
