Question 773927
The return trip is upstream, the lesser rate.  The downstream trip is the greater rate.


Let r = riverboat speed if no current.
Let c = speed of the current.


DIRECTION_______speed_________time______distance
UPSTREM_________r-c___________5__________30
DOWNSTREAM______r+c___________3__________30


Basic concept is rate*time=distance.

{{{(r-c)5=30}}} and {{{(r+c)3=30}}}
Two equations and two unknowns, r and c.  Solve the system.