The physical education teacher buys basketballs for the basketball players. If you buy 15 basketballs, you will have 220 yuan left. If you buy 20 basketballs, you will have 20 yuan left. How much is each basketball?
体育老师给篮球队员买篮球，买15个，还剩220元，买20个还剩20元，每个篮球多少元．
<gadget id="calculator">220 - 20</gadget>
<output>200</output>

<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<gadget id="calculator">200 / 5</gadget>
<output>40</output>

<result>40</result>