Answer:
If I am understanding your question, the total upstream is 8 miles and another 8 miles downstream.
Let s = the speed of the boat in still water
d = rt
8 = 5(s + 3) Â downstream
8 = 5s + 15 Â equation 1
8 = 5(s - 3) Â upstream
8 = 5s - 15 Â Â Add equation 1
8 = 5s + 15Â
16 = 10s   Divide both sides by 10.
s = 16/10 = 8/5 = 1.6 mph
Â