Chickens and rabbits are in the same cage. There are 20 heads and 62 feet. How many chickens are there?
鸡兔同笼，头共20个，足共62只，鸡有多少只．
<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<gadget id="calculator">62 - 40</gadget>
<output>22</output>

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

<gadget id="calculator">22 / 2</gadget>
<output>11</output>

<gadget id="calculator">20 - 11</gadget>
<output>9</output>

<result>9</result>