Question 874894
Boat speed	speed	x	km/h									
current     	speed	6	km/h									
..												
against 	current     	x-	6									
with	current     	x+	6									
..												
against	current     	8	hours									
with 	current     	6	hours									
Distance is same.  D=r*t												
8	(	x	-	6	)	=	6	(	x	+	6	)
8	x	-	48			=	6	x	+	36		
8	x	-	6	x	=		48	+	36			
2	x				=		84					
/	2											
x				=		42	km/h					
Boat speed	speed	=	42	km/h