Question 973894
This is a very common exercise question in uniform travel rates and deserves a generalized solution method.


RT=D, for rate, time, distance.


This table implies assigned variables.


______________speed_____________time___________distance
WITH__________r+w_________________v_______________d
AGAINST_______r-w_________________u_______________d


{{{v<u}}} according to the effect of the wind.


{{{system((r+w)v=d,(r-w)u=d)}}}
This is a system of two equations with the two unknown variables, r and w.  A bit of arithmetic and substitutions will make the system solvable.