The school breeding group raised 28 white and black rabbits, of which white rabbits accounted for (3/7). How many black rabbits are there?
学校饲养组养白兔和黑兔共28只，其中白兔占(3/7)．黑兔有多少只？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 - (3/7)</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">28 * (4/7)</gadget>
<output>16</output>

<result>16</result>