Let U = {1, 2, 3, 4, 5, 6, 7,8,9} A = {1, 2, 3, 5} B = {3, 4, 7} How many elements are in A' ∩ B ?

Answer 1

5 elements in A', 4 and 6 through 9

intersection with B is {4,7}

that's 2 elements in A' ^B