There are 30 chickens and rabbits in a cage, and they have 100 feet, so how many chickens are there in the cage?
一只笼子里共有鸡和兔30只，它们的脚共有100只，那么笼子里共有鸡多少只．
<gadget id="calculator">30 * 4</gadget>
<output>120</output>

<gadget id="calculator">120 - 100</gadget>
<output>20</output>

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

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<result>10</result>