How many chickens and rabbits are in the cage, 7 heads and 24 feet, how many chickens are there in the cage?
笼子里有鸡兔若干只，数头有7个，数脚有24只，笼子里有多少只鸡．
<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">24 - 14</gadget>
<output>10</output>

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

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<result>2</result>