The cruise ship goes down the current at 7 kilometers per hour, and goes upstream at 5 kilometers per hour. Two cruise ships with equal speeds in still water start from the same place at the same time. One goes upstream and returns; the other goes downstream and returns. As a result, they returned to the starting point at the same time after 2 hours. How much time during these 2 hours are the two ships heading in the same direction?
游船顺流而下，每小时前进7千米，逆流而上，每小时前进5千米．两条在静水中速度相等的游船同时从同一个地方出发．一个逆流而上，然后返回；一个顺流而下，然后返回．结果2小时后它们同时回到出发点．问在这2小时内有多少时间这两条船的前进方向相同？
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(5/7) * 120</gadget>
<output>600/7 = around 85.714286</output>

<gadget id="calculator">1 + (5/7)</gadget>
<output>12/7 = around 1.714286</output>

<gadget id="calculator">(600/7) / (12/7)</gadget>
<output>50</output>

<gadget id="calculator">120 - 50 - 50</gadget>
<output>20</output>

<result>20</result>