There are 3 white rabbits in a cage, and the number of black rabbits is 5 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5倍，黑兔有多少．
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<result>15</result>