Question 426400
Freight train	x mph	280	miles							
Express train	x +10 mph 200	miles							
														
t=d/r	
280/x=200/(x+10)+3		
280/x-200 /(x+10)=3		
LCD = x(x+10)							
Multiply by LCD														
280(x+10)-200x=3x(x+10)			
280x+2800-200*x	=3x^2+30
3X^2+80x-2770=0							
Find the roots of the equation by quadratic formula			
a=3	b=80	c=-2770							
b^2-4ac=6400+33240											
b^2-4ac=39640													
{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}														
{{{x1=(-b+sqrt(b^2-4ac))/(2a)}}}														
x1=(-80	+199.1)/6									
x1=19.85													
x2=(-80	-199.1)/6										
x2= -46.52													
Ignore negative value														
x=19.85	mph Freight train speed						
29.85	mph=Express train speed