There is a ship going downstream from port A to port B, and immediately going upstream from port B. On the way back to Port A, it takes 6 hours. It is known that the current speed is 5 kilometers per hour, and the ship travels 25 kilometers more in the first 3 hours than in the last 3 hours, then how many kilometers are the distance between the two ports of A and B?
有一艘船从甲港顺水而下行到乙港，马上又从乙港逆水．而上返回甲港，共用6小时．已知水流速度是每小时5千米，这艘船前3小时比后3小时多行25千米，那么甲、乙两港相距多少千米．
<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 * 7</gadget>
<output>35</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">25 / 10</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">35 * (5/2)</gadget>
<output>175/2 = around 87.5</output>

<result>175/2 = around 87.5</result>