A ship sails from city A to city B and arrives at a speed of 85 kilometers per hour for 4 hours. When returning from City B, due to the headwind, the speed of the ship slowed down by 17 kilometers per hour. How long does it take for the ship to reach City A?
一艘轮船从甲城开往乙城，以每小时85千米的速度行驶4小时到达．从乙城返航时由于逆风，轮船每小时的速度慢了17千米，轮船几小时才能到达甲城？
<gadget id="calculator">85 - 17</gadget>
<output>68</output>

<gadget id="calculator">4 / 68</gadget>
<output>1/17 = around 0.058824</output>

<gadget id="calculator">85 * (1/17)</gadget>
<output>5</output>

<result>5</result>