Question 441532
the distance is the same up and down stream 
upstream means against the current s-c 
downstream is with the current s+c

trip takes 4 48/60 hrs
r*t=d
(s-c)*u=35
(s+c)*d=35
u+d=4 48/60
s=15
we can substitute 15 for s
u=35-d
35-d for u
(15-c)*(35-d)=(15+c)*d
c=5/2 or 2.5 current
d=2
s=15
u=14/5= 2.8