There are 15 basketballs in the school sports room, equivalent to 60% of the number of volleyballs. The ratio of volleyballs to footballs is 5:4. How many footballs are there?
学校体育室有篮球15个，相当于排球数的60%，排球数与足球数的比是5：4，足球有多少个．
<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">15 / (3/5) / (5/4)</gadget>
<output>20</output>

<result>20</result>