Question 1145965
k, speed of the stream current
r, speed for crew if not in current
d, distance between A and B
d/3, distance between B and C


<pre>
               SPEED    TIME      DISTANCE

A to B          r-k       1        d

B to C          r+k      {{{1/5}}}      {{{d/3}}}
</pre>

What do you want to know how to do?  The description seems to make for three unknown numbers.   Some part of the description may have been omitted.