<PRE><B>Question 685702</B>
let the speed of boat in still water be x km/h

with current speed = (x+2) km/h

he covered a distance of 8 km

time 1 h 40 m= 1 2/3 hours = 5/3 hours

time = distance /speed 

{{{5/3 = 8/(x+2)}}}

cross multiply
5(x+2)=8*3

5x+10=24
5x=24-10
5x=14
x=14/5 
x=2.8 km/h speed of boat in still water.</PRE>