<PRE><B>Question 639753</B>
&lt;br&gt;&lt;font face=&quot;Tahoma&quot;&gt;Average, or mean, is just the total sum of the numbers, divided by the actual count of the numbers.&lt;br&gt;

So here we have an average of 20, given that we have 5 numbers.&lt;br&gt;

We just need to work backwards then.&lt;br&gt;

If our average is 20, and there are 5 numbers, then our total sum of the numbers is just 5*20, or 100.&lt;br&gt;

Since we know one of our numbers is 18,&lt;br&gt;

the sum of the other 4 numbers is simply 100-18, or 82 (which is choice C).&lt;br&gt;

I hope this helps!  :)&lt;br&gt;

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