Well, just going back, we could view this as all of the things in B with all of the things in A taken out of it or all of the things, the complement of A that happens to be in B. Let's think of it as the set B with all the things in A taken out of it. We start with set B, we have a 17, but a 17 is in set A so we have to take the 17 out. 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.