There are 20 bicycles and cars in the parking lot, and 64 wheels. How many bicycles are there?
停车场有自行车和小轿车共20辆，轮子共64个，那么自行车有多少辆．
<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<gadget id="calculator">80 - 64</gadget>
<output>16</output>

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

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<result>8</result>