Question 544922
Car		x	mph					
plane		90	faster	=	x+	90		
								
Car		240	miles					
plane		600	miles					
Car	time	=	plane		time			
t=d/r								
240	/	x	=	600	/(	x	+	90
cross multiply								
240	(	x	+	90	)	=	600	x
240	x	+	21600	=	600	x		
600	x	-	240	x	=	21600		
360	x	=	21600					
/	360							
x	=	60      	mph			Car		
								
150	mph	plane