Question 903939
Plane	speed	=x	mph					
wind  	speed	=y	mph					
against  	wind	2	hours					
with	wind	1 2/3	hours					
								
Distance against 		400	miles	distance with 		400	miles	
t=d/r	against	wind		-				
400      	/	(	x	-	y	)=	2      	
2      	(	x	-	y	)	=	1  2/ 3	
2      	x	-	2      	y	=	400      	....................1	
								
400      	/	(	x	+	y	)=	1  2/ 3	
1  2/ 3	(	x	+	y	)	=	400      	
1  2/ 3	x	+	1  2/ 3	y	=	400      	...............2	
Multiply (1) by	1  2/ 3							
Multiply (2) by	2      							
we get								
3  1/ 3	x	+	-3  1/ 3	y	=	666  2/ 3		
3  1/ 3	x	+	3  1/ 3	y	=	800      		
6  2/ 3	x	=	1466  2/ 3					
/	6  2/ 3							
x	=	220      	mph					
								
plug value of x in (1)				y				
2      	x		-2      	y	=	400      		
440      			-2      	-440      	=	400      		
-2      	y	=	400      					
-2      	y	=	-40      	mph				
	y	=	20      					
Plane	speed	220      	mph					
wind  	speed	20      	mph					
								
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