Four students collect stamps, Li Qiang 30, Zhang Feng 18, Wang Dong 20, Chen Liang 16, how many stamps each person collects on average.
四位同学收集邮票，李强30张、张峰18张、王东20张、陈亮16张，平均每人收集邮票多少张．
<gadget id="calculator">30 + 18 + 20 + 16</gadget>
<output>84</output>

<gadget id="calculator">84 / 4</gadget>
<output>21</output>

<result>21</result>