The store shipped 4 boxes of pencils, sold 20, and left 28. How many pencils are in each box?
商店运来4盒铅笔，卖出20支，还剩28支，每盒有多少支铅笔？
<gadget id="calculator">20 + 28</gadget>
<output>48</output>

<gadget id="calculator">48 / 4</gadget>
<output>12</output>

<result>12</result>