Question 1194344
Given universal set U= {10,20,30,40,50,60,70,80,90} 
with subsets A= {20,40,60,80} and B= {30,60,90}, 
find A ∩ B
<pre>
Substitute the sets for the letters:

A ∩ B

{20,40,60,80} ∩ {30,60,90}

The symbol ∩ is for intersection, which means to
make a set that contains only the elements which
are common to both sets.  So the answer is

{60}  

That's because 60 is the only element in common 
to both sets.

Edwin</pre>