Teacher Wang brought 100 yuan. After buying 4 identical basketballs, there is 28 yuan left. How much is each basketball on average?
王老师带了100元钱，买了4只同样的篮球以后，还剩28元，平均每只篮球多少元？
<gadget id="calculator">100 - 28</gadget>
<output>72</output>

<gadget id="calculator">72 / 4</gadget>
<output>18</output>

<result>18</result>