Question 671719
Boat  	speed	=x	mph					
current     	speed	=y	mph					
againstcurrent x-y		15	hours					
with current x+y		5	hours					
								
Distance = 		120	miles		distance=		120	
t=d/r	against	current     		-				
120.00	/	(	x		y	)=	15.00	
				y				
15.00	x	-	-15.00		=	120.00	....................1	
downstream				+				
120.00	/	(	x	y	y	)=	5.00	
5.00	(	x	+	y	)	=	120.00	
5.00	x	+	5.00		=	120.00	...............2	
Multiply (1) by	1.00							
Multiply (2) by	3.00							
we get				y				
15.00	x	+	-15.00	y	=	120.00		
15.00	x	+	15.00		=	360.00		
30.00	x	=	480.00					
/	30.00							
x	=	16	mph					
								
plug value of x in (1)				y				
15	x		-15	y	=	120		
240			-15	-240	=	120		
-15	y	=	120					
-15	y	=	-120	mph				
	y	=	8					
	Boat  	16	mph					
	current     	8	mph