There are some chickens and rabbits in the cage. Xiaofang counts the number of chickens and rabbits from the bottom of the cage. There are 120 feet in total. In addition, knowing that the number of chickens is twice that of rabbits, ask how many chickens there are.
笼子里养了一些鸡和兔，小芳从笼子下方数了下鸡兔一共有120只脚，另外知道鸡的只数是兔的2倍，问鸡有多少只．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">4 + 4</gadget>
<output>8</output>

<gadget id="calculator">120 / 8</gadget>
<output>15</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<result>30</result>