Question 816589
boat   	speed	x	mph				
current     	speed	9	mph				
..							
against	current     	x	-	9	mph		
with	current     	x   	+	9	mph		
							
Distance against	current     	120					
Distance with	current     	180					
Time = same	equate the time against with time with current						
t=d/r							
120	/(x-	9	)=	180	/(x+	9	)
120	*(x+	9	)=	180	*(x-	9	)
120	x  	+	1080	=	180	x	-1620
120	x  	-180	x   	=	-1620	+	-1080
-60	x  	=	-2700				
/	-60						
	x=	45	mph				
m.ananth@hotmail.ca