Question 508313
Boat	speed=	x	mph					
current	speed=	y	mph					
with 	current speed=	(x+y) 						
against 	current speed=	(x-y) 						
d=	72		with	current				
72	/	(x+y) 	=	3				
divide by 	3							
24	/	(x+y) 	=	1				
(x+y) 	=	24	............1					
d=	=	48	against 	current				
27/(x-y) 	=	3						
divide by 	3							
48	/(x-y)	=	3					
	x	-		y	=	16	.............2	
add up (1) & (2)								
2	x	=	40					
/	2							
x=	20	mph	speed of	Boat	in still 	water		
plug value of x in (1)								
we get 	y= 	4	mph	speed of	current