Question 834390
r*t=d
t=d/r
a+b=8,
a*(x+c))+b*(x-c)=40,
a*(x+c))=b*(x-c),
5/(c+x)=3/(x-c)
a = 3,   b = 5,   c = 4/3,   x = 16/3
speed in still water 16/3
current speed 4/3