Question 568185
plane	speed=x 		mph					
wind	speed=y		mph					
with	wind	Speed =		(x+y)				
against	wind	speed=		(x-y)				
d=	4200							
4200	/	(x+y=	6				
divide by 	6							
700	/	(x+y)=		1				
x+	y	700	............1					
d=		4200						
4200	/(x-y)=	7						
divide by 	7							
600	/(x-y)	=	7					
	x-y	=	600.00	.............2	
add up (1) & (2)								
2	x	=	1300					
/	2							
x=	650	mph	speed of	plane	in still air			
plug value of x in (1)								
we get 	y= 	50	mph	speed of	wind