The library originally had 715 comic books, 378 were lent out, and 169 were returned. How many are there now?
图书馆原有连环画715本，借出378本，还回169本，现在又多少本？
<gadget id="calculator">715 - 378</gadget>
<output>337</output>

<gadget id="calculator">337 + 169</gadget>
<output>506</output>

<result>506</result>