The kindergarten bought 1 football and 5 small balls, which cost 30 yuan in total, 10 yuan for a small football, how much is a small ball? How many columns.
幼儿园买了1个足球和5个小皮球，一共花了30元，一个小足球10元，一个小皮球多少钱？列式多少．
<gadget id="calculator">30 - 10</gadget>
<output>20</output>

<gadget id="calculator">20 / 5</gadget>
<output>4</output>

<result>4</result>