There are 100 chickens and rabbits, and the number of chicken feet is 40 less than that of rabbits. How many rabbits are there?
鸡兔共100只，鸡脚比兔脚少40只，兔有多少只．
<gadget id="calculator">2 * 100</gadget>
<output>200</output>

<gadget id="calculator">200 + 40</gadget>
<output>240</output>

<gadget id="calculator">4 + 2</gadget>
<output>6</output>

<gadget id="calculator">240 / 6</gadget>
<output>40</output>

<result>40</result>