There is a flock of chickens and rabbits, the total number of legs is 60 more than twice the total number of heads, how many rabbits are there?
有一群鸡和兔，腿的总数比头的总数的2倍多60，兔子有多少只．
<gadget id="calculator">60 / 2</gadget>
<output>30</output>

<result>30</result>