Chickens and rabbits are in the same cage. There are 30 heads and 96 feet. How many chickens are there?
鸡兔同笼，有30个头，96只脚，鸡有多少只．
<gadget id="calculator">30 * 2</gadget>
<output>60</output>

<gadget id="calculator">96 - 60</gadget>
<output>36</output>

<gadget id="calculator">4 - 2</gadget>
<output>2</output>

<gadget id="calculator">36 / 2</gadget>
<output>18</output>

<gadget id="calculator">30 - 18</gadget>
<output>12</output>

<result>12</result>