The library has lent out 456 books, and there are 207 books left, and now 285 books have been returned. How many books are there in the library now?
图书室借出456本图书，还剩207本，现在又还回285本，图书室里现在有多少本？
<gadget id="calculator">207 + 285</gadget>
<output>492</output>

<result>492</result>