There are 50 chickens and rabbits in the same cage, and they have 120 feet. How many rabbits are there?
鸡兔同笼共有50只，它们的脚共有120只．兔有多少只．
<gadget id="calculator">50 * 2</gadget>
<output>100</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>