The school buys 28 soccer balls for 980 yuan, and buys 23 volleyballs for 966 yuan. On average, how much is each volleyball more expensive than each soccer ball?
学校买28个足球共用去980元，买23个排球共用去966元．平均每个排球比每个足球贵多少元？
<gadget id="calculator">966 / 23</gadget>
<output>42</output>

<gadget id="calculator">980 / 28</gadget>
<output>35</output>

<gadget id="calculator">42 - 35</gadget>
<output>7</output>

<result>7</result>