The speed of a boat in still water is 5 kilometers per hour. Now it travels to and from a certain river. It is known that the speed when going up (going against the water) is (3/5) of the speed when going down (going along the water). The speed of the water flow is (2/3) of the speed of the water flow in the downward direction. Find the speed of the water flow in the upward direction.
一船在静水中的速度是每小时5千米，现在往返于某河中，已知上行时(逆水而行)的速度是下行时(顺水而行)的速度的(3/5)，又上行的水流速度是下行时水流速度的(2/3)，求上行的水流速度．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">5 * (3/5)</gadget>
<output>3</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">3 * (3/5)</gadget>
<output>9/5 = around 1.8</output>

<gadget id="calculator">2 + (9/5)</gadget>
<output>19/5 = around 3.8</output>

<gadget id="calculator">2 / (19/5)</gadget>
<output>10/19 = around 0.526316</output>

<gadget id="calculator">2 * (10/19)</gadget>
<output>20/19 = around 1.052632</output>

<result>20/19 = around 1.052632</result>