There are 20 cars and tricycles in the parking lot, and there are 68 wheels in total. How many of them are there?
停车场小轿车和三轮车共20辆，总共有68个轮子，其中三轮车有多少辆．
<gadget id="calculator">20 * 3</gadget>
<output>60</output>

<gadget id="calculator">68 - 60</gadget>
<output>8</output>

<gadget id="calculator">4 - 3</gadget>
<output>1</output>

<gadget id="calculator">8 / 1</gadget>
<output>8</output>

<gadget id="calculator">20 - 8</gadget>
<output>12</output>

<result>12</result>