The breeding group raised several lovely little rabbits. The number of white rabbits is black rabbits (2/5), the number of gray rabbits is white rabbits (1/3), and there are 2 gray rabbits. Do you know how many black rabbits there are?
饲养小组养了几只可爱的小兔子．白兔的只数是黑兔的(2/5)，灰兔的只数是白兔的(1/3)，灰兔有2只．你知道黑兔有多少只吗？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">2 / (1/3) / (2/5)</gadget>
<output>15</output>

<result>15</result>