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 )