The school bought some balls. Among them, volleyball accounted for 20%, football accounted for (3/4), bought 15 footballs, how many volleyballs did the school buy?
学校买来一些球．其中排球占20%，足球占(3/4)，买来足球15个，学校买来排球多少个？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

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

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">20 * (1/5)</gadget>
<output>4</output>

<result>4</result>