Arthur knows that he needs to finish 800 pages of reading over the summer. He has read 80% of a 500-page book and 1/5 of a 1000 page book. How many more pages does he need to reach to meet his goal?
He read 400 pages from the 500 page book because 500 x .8 = 
<gadget id="calculator">500*.8</gadget>
<output>400</output>
400.
He read 200 pages from the 1000 page book because 1000 x (1/5) = 
<gadget id="calculator">1000*(1/5)</gadget>
<output>200</output>
200.
He has read 600 pages in total.
He needs to read 200 more pages to reach 800 pages because 800 - 600 = 
<gadget id="calculator">800-600</gadget>
<output>200</output>
200.

<result>200</result>