Question 1031806
Bob paddled against current for 2 hrs. and then with current for 1 hr. and rested. 
let Bob's speed in still water be x
with current his speed will be x+3  mph
with current he paddled for (x+3) * 1

against current his speed will be x-3 mph
against current he paddled f or (x-3)*2

Rick with current for 1.5 hrs.
 let Rick's speed in still water be y
with current his speed will be y+3  mph
with current he paddled for (y+3) * 1.5


Rick paddled against current for 2.5 hrs. 

against current his speed will be y-3 mph
against current he paddled f or (y-3)*2.5



If they paddled a total of 9.5 miles against the current
(x-3)*2 +(y-3)*2.5 = 9.5
2x-6 +2.5y -7.5 =9.5
2x+2.5y = 23...........................(1)

 and 20.5 miles  with the current

(x+3) * 1+ (y+3) * 1.5=20.5

x+3 +1.5y +4.5 =20.5

x+1.5y=13.......................(2)

2.00	x	+	2.50	y	=	23.00	.............1	
								
1.00	x	+	1.50	y	=	13.00	.............2	
Eliminate	y							
multiply (1)by		-1.50						
Multiply (2) by		2.50						
-3.00	x		-3.75	y	=	-34.50		
2.50	x	+	3.75	y	=	32.50		
Add the two equations								
-0.50	x				=	-2.00		
/	-0.50							
x	=	4.00						
plug value of			x	in (1)				
2.00	x	+	2.50	y	=	23.00		
8.00		+	2.50	y	=	23.00		
			2.50	y	=	23.00		-8.00
			2.50	y	=	15.00		
				y	=	6.00		
x=	4.00	mph	Bob's 	speed				
y=	6.00	mph	Rick's	speed	

			
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