Question 534944
Train I	x 	mph						
Train II	x+	12	mph					
..								
They are moving away from each other								
								
So add up their speed.								
								
combined speed = x+		1	x	+	12			
(	2	x	+	12	) 			
Time = 	6	hours						
Distance =   	780	miles						
Distance = speed * time								
(	2	x		12	)*	6	=	780
12	x 	+	72	=	780			
12	x 	=	780	+	-72			
12	x 	=	708					
/	12							
x=	59	mph	Train I					
Train II	59	+	12	=	71	mph		

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