Then we have a 19, but there's a 19 in set A so we have to take the 19 out. Then we have a 6. We don't have to take a 6 out of B because the 6 is not in set A so we're left with just the 6. This would be just the set with a single element in it, set 6. Now, let me ask another question. What would the relative complement of A in A be? This is the same thing as A minus A.