The school bought 36 small balls, four times as many as footballs. How much is the difference between a small ball and a football?
学校买来小皮球36只，是买来足球的4倍．小皮球与足球相差多少只？
<gadget id="calculator">36 / 4</gadget>
<output>9</output>

<gadget id="calculator">36 - 9</gadget>
<output>27</output>

<result>27</result>