There are 20 bicycles and tricycles and 44 wheels, how many of them are there?
自行车和三轮车共20辆，轮子共44个，其中三轮车有多少辆．
<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<gadget id="calculator">44 - 40</gadget>
<output>4</output>

<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">4 / 1</gadget>
<output>4</output>

<result>4</result>