After the library borrowed 354 books, there are still 506 books left, and now 249 books are returned. How many books are there in the library now?
图书馆借出354本书后，还剩下506本，现在又还来249本，现在图书馆里有多少本书？
<gadget id="calculator">506 + 249</gadget>
<output>755</output>

<result>755</result>