Find the GCF between 24 and 36 by prime factorization:
24 = 2 * 2 * 2 * 3
36 = 2 * 2 * 3 * 3
Now, notice that the common between the prime factorization of both numbers are 2*2*3 which is what we call Greatest Common Factor and over here equal to 12.
Take 12 as a common factor in the above addition:
24 + 36 = 12 ( 2 + 3 )