Question 468914
given U={15,16,17,18,19,20,21,22,23,24,25}, A={16,18,20,22}B={17,19,20,23,24}
find A' ᑎ B'

<pre>
A' is the set of all elements of U that are not elements of A,

so A' = {15,17,19,21,23,24,25}.

B' is the set of all elements of U that are not elements of B,

so B' = {15,16,18,21,22,25}.

Therefore 

A' &#5198; B' = {15,17,19,21,23,24,25} &#5198; {15,16,18,21,22,25}

&#5198; means to get the set of only those elements that are in 
common to the sets on both sides of the symbol &#5198;.  There are
only three elements in common to both sets. 

A' &#5198; B' = {15,21,25}
 
Edwin</pre>