Boss Li rented a total of 20 large and small vehicles, and he had to transport 180 tons of goods at a time. Each large vehicle is 10 tons, and each small vehicle is 6 tons. How many small vehicles did Boss Li rent?
李老板租用了大、小车共20辆，一次要运完180吨货物．每辆大车载10吨，每辆小车载6吨，李老板租用了小车多少辆．
<gadget id="calculator">10 * 20</gadget>
<output>200</output>

<gadget id="calculator">200 - 180</gadget>
<output>20</output>

<gadget id="calculator">10 - 6</gadget>
<output>4</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<result>5</result>