The number of white rabbits is 20% less than the number of black rabbits, that is, the number of black rabbits is more than the number of white rabbits.
白兔的只数比黑兔只数少20%，也就是黑兔的只数就比白兔只数多多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/5) / (4/5)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>