Question 512188
plane speed	=	500	mph										
wind speed	=	x	mph																							
speed against	wind	500	-	x								11.7	
speed with	current	500	+	x									
													
Distance against	current	1580	m 										
Distance with 	current	2420	m 										
													
t=d/r	time against = time with												
1580/(	500	-x)=	2420	/(500	+	x	)
1580	(	500	+	x	)=	2420	(500-x)			
790000	+	1580	x	=	1210000	-	2420	x 					
2420	x	1580	x	=	420000								
4000	x	=	420000										
/	4000												
x 	=	105	mph	wind speed