There are 10 bicycles and tricycles with 24 wheels. How many tricycles are there?
自行车和三轮车共有10辆，共有24个轮子，三轮车有多少辆．
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">24 - 20</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>