The parking lot stipulates that a management fee of 2.5 yuan will be charged for 1 hour of parking, and a management fee of 3 yuan per hour will be charged after parking for more than 1 hour. Uncle Li paid a management fee of 17.5 yuan. How many hours has he been parked in the parking lot?
停车场规定，停车1小时收2.5元管理费，停车超过1小时后，每小时收3元管理费．李叔叔交了17.5元的管理费．他在停车场停了多少小时？
<gadget id="calculator">17.5 - 2.5</gadget>
<output>15</output>

<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<result>6</result>