Xiaojun has 21 cards and Xiaoqing has 39 cards. After Xiaoqing gives Xiaojun a few cards, they will have the same number of cards?
小军有21张卡片，小青有39张卡片，小青给小军几张后，他俩的卡片就会一样多？
<gadget id="calculator">21 + 39</gadget>
<output>60</output>

<gadget id="calculator">60 / 2</gadget>
<output>30</output>

<gadget id="calculator">39 - 30</gadget>
<output>9</output>

<result>9</result>