Question 498948
Plane   	speed	=x	mph					
Wind   	speed	=y	mph					
against wind x-y		18.00	hours					
with windx+y		9.00	hours					
								
Distance = same=		864	miles					
t=d/r								
864	/	(	x	-	y	)=	18.00	
18	(	x	-	y	)	=	864.00	
18	x		-18	y	=	864	....................1	
864	/	(	x	+	y	)=	9.00	
9.00	(	x	+	y	)	=	864	
9.00	x	+	9.00	y	=	864	...............2	
Multiply (1) by 	1.00							
Multiply (2) by	2.00							
we get								
18	x	+	-18	y	=	864		
18	x	+	18	y	=	1728		
36	x	=	2592					
/	36							
x 	=	72	mph					
								
plug value of x in (1)								
18	x		-18	y	=	864		
1296			-18	y	=	864		
-18	y	=	864	-1296				
-18	y	=	-432					
	y	=	24	mph