I am studying Proof, Logic, and Conjecture by Robert Wolf. A great textbook but the solutions seem to be nowhere.
In the chapter on relations, this question appears:
Let A={1,2,3}, B={2,5}
How many elements are in
(A $ \times $ B) - (A $ \cup $ B)
?
(I’m not even sure how to perform this operation since it seems like a set of ordered pairs minus a set of single digits doesn’t appear to be legal, in my opinion. I guess I don’t understand how these concepts are actually related yet. Any guidance? How can this operation be done?)