Question 424761
Norma		x	mph
Marietta 	15	faster
			
Norma		12	miles
Marietta 	36	miles
....
Norma	time	=Marietta 		time			
								
12/x=36/	(x+15)
cross multiply								
12(x+15)	=36x
12x+180	=36x		
36x-12x	=180		
24x=180					
/24							
x=7  1/ 2mph Norma speed