Ali had a stock of 800 books in his Room. He sold 60 on Monday, 10 on Tuesday, 20 on Wednesday, 44 on Thursday and 66 on Friday. How many books were not sold?
We look first for the total number of books that were sold: 60 + 10 + 20 + 44 + 66 = 
<gadget id="calculator">60+10+20+44+66</gadget>
<output>200</output>
200 books.
So the total number of books that were not sold is: 800 - 200 = 
<gadget id="calculator">800-200</gadget>
<output>600</output>
600 books.

<result>600</result>