Question

Which is the intersection of the sets {1, 4, 8, 9} and {2, 4, 7, 9, 11}?

{4, 9}

{1, 2, 7, 8, 11}

null set

{1, 2, 4, 7, 8, 9, 11}

Answer 1

7
Here is a tip:
so you have {1 2 4 7 8 9 11} Take your fingers on each end and cover each number till you get you the middle.