Question 568269
Boat 	speed	=x	mph					
current   	speed	=y	mph					
against  current x-y		12.00	hours					
with current x+y		4.00	hours					
								
Distance = same=		108	miles					
t=d/r								
108	/	(	x	-	y	)=	12.00	
12	(	x	-	y	)	=	108.00	
12	x		-12	y	=	108	....................1	
108	/	(	x	+	y	)=	4.00	
4.00	(	x	+	y	)	=	108	
4.00	x	+	4.00	y	=	108	...............2	
Multiply (1) by 	1							
Multiply (2) by	3							
we get								
12	x		-12	y	=	108		
12	x	+	12	y	=	324		
24	x	=	432					
/	24							
x 	=	18	mph					
								
plug value of x in (1)								
12	x		-12	y	=	108		
216			-12	y	=	108		
-12	y	=	108	-216				
-12	y	=	-108					
	y	=	9					
The speed of  	Boat 	=	18	mph				
The speed of  	current   	=	9	mph				
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