There are 20 heads and 48 legs in the same cage as chickens and rabbits. How many rabbits are there?
鸡兔同笼，有20个头，48条腿，其中兔子有多少只．
<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<gadget id="calculator">80 - 48</gadget>
<output>32</output>

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

<gadget id="calculator">32 / 2</gadget>
<output>16</output>

<gadget id="calculator">20 - 16</gadget>
<output>4</output>

<result>4</result>