The distance between two cities, A and B, is 612 kilometers, and it takes 12 hours for a car to drive from city A to city B. Speed up 17 kilometers per hour when returning. How many hours will it take to return?
甲、乙两个城市相距612千米，一辆小汽车从甲城开往乙城用了12小时．返回时每小时加快17千米．返回要用多少小时？
<gadget id="calculator">612 / 12</gadget>
<output>51</output>

<gadget id="calculator">51 + 17</gadget>
<output>68</output>

<gadget id="calculator">612 / 68</gadget>
<output>9</output>

<result>9</result>