If a ship sails along the water at a speed of 18 km/h and against the current at 15 km/h, what is the speed of the water in this section of water in km/h?
一艘轮船在一段水域中顺水航行的速度为18千米/小时，逆水航行的速度为15千米/小时，则这段水域中水流的速度为多少千米/小时．
<gadget id="calculator">18 - 15</gadget>
<output>3</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>