There are several chickens and rabbits, the number of chickens and rabbits is the same, and the total number of legs of rabbits is 30 more than the total number of legs of chickens. May I ask: How many chickens and rabbits are there?
有若干只鸡和兔，其中鸡和兔的数量一样多，兔的总腿数比鸡的总腿数多30条．请问：鸡、兔各有多少只？
<gadget id="calculator">4 - 2</gadget>
<output>2</output>

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

<result>15</result>