The speed of boat A in still water is 10 kilometers per hour, and the speed of boat B in still water is 20 kilometers per hour. Two boats start from port A and go upstream, the current speed is 4 kilometers per hour, and boat B returns immediately after arriving at port B. It took 2 hours from the departure to the meeting of the two ships. How many kilometers is the distance between the two ports of A and B?
甲船在静水中的船速是每小时10千米，乙船在静水中的船速是每小时20千米．两船从A港出发逆流而上，水流速度是每小时4千米，乙船到B港后立即返回．从出发到两船相遇用了2小时，问A、B两港相距多少千米？
<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">1 + 4</gadget>
<output>5</output>

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

<gadget id="calculator">(5/8) * (1/5)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">20 - 4</gadget>
<output>16</output>

<gadget id="calculator">6 / 16</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">(1/8) + (3/8)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / (1/2)</gadget>
<output>4</output>

<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<result>24</result>