There are 40 chickens and rabbits in total. If you count 130 feet of chickens and rabbits, how many rabbits are there?
鸡、兔共40只，数出鸡、兔的脚共有130只，则兔有多少只．
<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<gadget id="calculator">130 - 80</gadget>
<output>50</output>

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

<gadget id="calculator">50 / 2</gadget>
<output>25</output>

<result>25</result>