A boat travels downstream from Port A to Port B, and immediately travels upstream from Port B back to Port A. It takes 8 hours. It is known that the travel along the current is 20 kilometers longer than that against the current, and it is also known that the travel in the first 4 hours is 60 kilometers longer than the last 4 hours. Then, how many kilometers are the distance between A and B?
一船从甲港顺水而下到乙港，马上又从乙港逆水行回甲港，共用了8小时．已知顺水每小时比逆水多行20千米，又知前4小时比后4小时多行60千米．那么，甲、乙两港相距多少千米．
<gadget id="calculator">50 - 30</gadget>
<output>20</output>

<gadget id="calculator">60 / 20</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">8 - 3</gadget>
<output>5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/3) - (1/5)</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">20 / (2/15)</gadget>
<output>150</output>

<result>150</result>