<PRE><B>Question 248884</B>
Here we are dealing with sets and set operations.  Sets are named using capital letters and the set elements are enclosed in brackets.&lt;br&gt;

a.) A U B is also known as the Union of set A and set B.  The Union of 2 sets means just picking out all the set elements which are found in set A OR in set B.  Essentially, every element contained in set A or set B is found in set A U B.&lt;br&gt;

We can then easily see that &lt;b&gt;A U B = {1,2,3,4,5,6,7,8,10,12}&lt;/b&gt;&lt;br&gt;

Notice that we do not need to put the elements 5 and 6 in the new set twice.  Once will suffice.  Think of the Union of sets as an umbrella which will catch all of the set elements in it once.&lt;br&gt;

b.) For part b, we will use this symbol @ to indicate A Intersect B, which will in turn look like A @ B.&lt;br&gt;

The intersection of 2 sets essentially means finding the set elements which are contained in BOTH set A AND in set B.  We can easily scan the 2 sets and see that the only elements contained in both A and B are the numbers 5 and 6.&lt;br&gt;

So &lt;b&gt;A @ B = {5,6}&lt;/b&gt;&lt;br&gt;&lt;br&gt;  </PRE>