There are 3 white rabbits in a cage, and the number of black rabbits is 4 times that of white rabbits. How many black rabbits are there?
笼子里有白兔3只，黑兔的只数是白兔的4倍，黑兔有多少只．
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<result>12</result>