Question

Find A n B if A={5, 10, 15, 20} and B={10, 2O, 25, 30}

THAT N IS AN UPSIDEDOWN U, DON'T KNOW WHAT THAT MEANS

Answer 1

http://www.solving-math-problems.com/math-symbols-set-intersection.html

It means intersection
which elements are in both sets? (overlap)
5 no
10 yes
15 no
20 yes
25 no
30 no
so
{ 10,20}

Answer 2

The "upside down U" stands for intersection.
It means that you are looking for all elements which are common to both A and B
A ∩ B = {10,20)