Ineed with finding the gcf (greatest common factor) of 72,48

First, find all the factors of the two numbers (separately):
72: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, and 72
48: 1, 2, 3, 4, 6, 8, 12, 16, 24, 48
The numbers in bold are factors of both 72 and 48.
Find the greatest one (out of the numbers in bold). 24 is the GCF.

The factors of  72  are  1,  2,  3,  4,  6,  8,  9,  12,  18,  24,  36, and  72 .

The factors of  48  are  1,  2,  3,  4,  6,  8,  12,  16,  24, and  48 .

The factors common to both  72  and  48  are  1,  2,  3,  4,  6,  8,  12, and  24 .

The greatest one of those is  24 . 

31 is prime. and it’s prime factorization is just 31.