Question 499411
The speed of the boat going upstream (against the current) = 
s -c : the speed in still water - the speed of the current
.
d = rt is the distance equation
d = 117 (given)
.
t = 6.5 hr (given)
.
c = 5 mph (given)
.
Substitute the knows (givens):
.
117 = (s-5)*6.5
.
Divide both sides by 6.5
18 = (s-5)
18 = s -5
.
Add 5 to both sides
23 = s
s = 23
.
The speed of the boat in still water is 23.
.
Done.