The students in the biology group raised 20 white rabbits, and the black rabbits raised were 25% less than the white rabbits. How many black rabbits did they raise?
生物小组的同学们养了20只白兔，养的黑兔比白兔少25%，养了多少只黑兔．
<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">20 * (4/5)</gadget>
<output>16</output>

<result>16</result>