Intersection and Union?

Question

Ok in my algebra class, I am doing intersection and union. I am not sure what i would do:
A={4,5,6,7}
B={5,6}
C={8,9,10}
D={6,9}

So what would I do if it was

A intersection B union C intersection D

Sorry I cant get the upside down u's on my computer
Thanks to anyone who can help!

Answer 1

Wow, good question. I don't know what the hierarchy is for ∩ and ∪. But IF they have the same hierarchy, then I'd work it left to right:

((A ∩ B) ∪ C) ∩ D
= ({5,6} ∪ C) ∩ D
= {5,68,9,10} ∩ D
= {6,9}

Answer 2

AnBuD consists of those elements in A and B OR D.

Looking at A and B, AnB = {5,6}, as these are the only elements that appear in both A and B.

Thus AnBuD is those elements that appear in AnB OR in D. So, AnBuD = {5,6,9} (you don't repeat the 6 because although it appears in both AnB and D, elements in a set cannot be repeated)