After the library has lent 351 books, there are still 509 books left, and now 176 books have been bought. How many books are there in the library now?
图书室借出351本后，还剩下509本，现在又买来176本．现在图书室里有多少本书？
<gadget id="calculator">509 + 176</gadget>
<output>685</output>

<result>685</result>