The parking fee standard of a certain parking lot is: 5 yuan within 1 hour, and 2.5 yuan for each hour after more than 1 hour. Uncle Li paid 25 yuan after parking in this parking lot. How many hours did he park in total?
某停车场停车收费标准是：1小时以内收费5元，超过1小时后，每超过1小时加收费2.5元．李叔叔在这个停车场停车后交了25元，他共停车多少小时？
<gadget id="calculator">25 - 5</gadget>
<output>20</output>

<gadget id="calculator">20 / 2.5</gadget>
<output>8</output>

<gadget id="calculator">1 + 8</gadget>
<output>9</output>

<result>9</result>