The library originally had 498 books, 245 were borrowed, and 217 were returned. How many books are there now?
图书馆原有图书498本，借走了245本，又还回了217本，现在有多少本？
<gadget id="calculator">498 - 245</gadget>
<output>253</output>

<gadget id="calculator">253 + 217</gadget>
<output>470</output>

<result>470</result>