After the school library borrowed 360 books, there were 405 books left, and now 278 books have been returned. How many books are there in the library now?
学校图书馆借出360本图书后，还剩405本，现在又还回278本．现在图书馆里有多少本书？
<gadget id="calculator">405 + 278</gadget>
<output>683</output>

<result>683</result>