A ship travels between two ports, A and B, which are 240 kilometers apart. The upstream speed is 18 kilometers per hour, and the downstream speed is 26 kilometers per hour. The speed of a motorboat is 20 kilometers per hour. How many hours does it take for the motorboat to travel between the two ports?
一只轮船往返于相距240千米的甲、乙两港之间．逆水速度是每小时18千米，顺水速度是每小时26千米．一艘汽艇的速度是每小时20千米．这艘汽艇往返于两港之间共需多少小时？
<gadget id="calculator">26 - 18</gadget>
<output>8</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">20 + 4</gadget>
<output>24</output>

<gadget id="calculator">240 / 24</gadget>
<output>10</output>

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

<gadget id="calculator">240 / 16</gadget>
<output>15</output>

<gadget id="calculator">10 + 15</gadget>
<output>25</output>

<result>25</result>