Question 867972
Let r = the man's rate in still water.  His rate downstream is r+2 km/hr and his rate upstream is r-2 km/hr.  The problem description forces the reader to infer that the time  quantity described is for a specific distance.  This is a fault in the given problem description, but would be a very likely meaning.


______________rate__________time__________distance
DOWN__________r+2___________t______________d
UP____________r-2___________2t_____________d


BEFORE DOING THE ALGEBRA STEPS, I THOUGHT: At best, you will have one equation and still two unknown variables.


BUT AFTER  DOING THESE STEPS:
{{{(r+2)t=(r-2)*2t}}}
{{{rt+2t=2rt-4t}}}
{{{rt-2rt=-4t-2t}}}
{{{-rt=-6t}}}
{{{highlight(r=6)}}}