Question 587636
Boat speed	=	8	km/h										
current  speed	=	x	km/h										
													
speed against	current	8	-	x									
speed with	current	8	+	x									
													
Distance against	current	5	km										
Distance with	current	10	km										
													
t=d/r	time against = time with		current										
5/(8-x)=10/(8+x)
5(8+x)=	10(8-x)			
40+5x=80-10x					
10x+5x	=80-40						
15x=40										
/	15												check
x	=	2.67	km/h	current  speed