There are 78 story books in the library, 37 are borrowed in the morning, and 28 are returned in the afternoon. How many story books are there in the library now?
图书馆有故事书78本，上午借走37本，下午又还回28本，现在图书馆有故事书多少本？
<gadget id="calculator">78 - 37</gadget>
<output>41</output>

<gadget id="calculator">41 + 28</gadget>
<output>69</output>

<result>69</result>