A． The distance between the two cities of B is 180 km. The speed of a passenger ship in still water is 25 km/h. From A to B is sailing along the water. The water speed is 5 km/h. Ask the ship to travel between the two places How long will it take?
A．B两城之间相距180千米，一艘客轮在静水中的速度是25千米/时，从A到B是顺水航行，水速为5千米/时，求轮船往返于两地之间共需多长时间？
<gadget id="calculator">25 + 5</gadget>
<output>30</output>

<gadget id="calculator">180 / 30</gadget>
<output>6</output>

<gadget id="calculator">25 - 5</gadget>
<output>20</output>

<gadget id="calculator">180 / 20</gadget>
<output>9</output>

<gadget id="calculator">6 + 9</gadget>
<output>15</output>

<result>15</result>