Question 935985
This table of data implies the variables.


________________rate___________time__________distance
UPSTREAM________r-s____________u_____________d
BACK____________r+s____________v_____________d


KNOWN:  u,v,d.
Rule for uniform travel rates, RT=D rate time distance.


{{{(r-s)*u=d}}}, and {{{(r+s)*v=d}}};
Those are two linear equations in the two unknown variables, r and s.


Solve for r and s, and then substitute u=3, v=2, d=12.