Question 428525
plane speed		x	mph				
wind speed		10	mph				
..							
against wind x-10mph		
with wind  x+10	mph		
							
Distance against wind	380					
Distance with tail wind	420					
Time = same							
380/(x-	10)=	420/(x+	10)
380*(x+	10)=	420*(x-	10)
380x  	+3800	=420x-4200
420x  	-380x   	=4200+3800
40x  	=8000				
/40						
x=	200 mph