General Idea:
When simplifying a rational expression, we need to do the below steps:
(i) Factor the Denominator of each fraction
(ii) Identify the Least Common Denominator (It is the product of prime factors involved with its highest exponent)
(iii) Identify and rewrite the equivalent fraction with the desired LCD.
(iv) Once the denominator are same, Combine the numerator.
Applying the concept:
What is the difference x/x^2-16-3/x-4
I assume that you mean to type the expression 
Step 1: Factoring 

Step 2: Identifying the LCD, we get 
Step 3: Rewriting the second fraction by multiplying x+4 on both top and bottom of second fraction so that we get the LCD.
![\frac{x}{x^2-16}-\frac{3}{x-4}=\frac{x}{(x+4)(x-4)} -\frac{3*(x+4)}{(x-4)*(x+4)} Step 4: Combine like terms since the denominators are same[tex] \frac{x-3(x+4)}{(x+4)(x-4)} =\frac{x-3x-12}{(x+4)(x-4)}=\frac{-2x-12}{(x+4)(x-4)} =\frac{-2(x+6)}{(x+4)(x-4)}](https://tex.z-dn.net/?f=%20%5Cfrac%7Bx%7D%7Bx%5E2-16%7D-%5Cfrac%7B3%7D%7Bx-4%7D%3D%5Cfrac%7Bx%7D%7B%28x%2B4%29%28x-4%29%7D%20%20%20-%5Cfrac%7B3%2A%28x%2B4%29%7D%7B%28x-4%29%2A%28x%2B4%29%7D%20%3C%2Fp%3E%3Cp%3EStep%204%3A%20Combine%20like%20terms%20since%20the%20denominators%20are%20same%3C%2Fp%3E%3Cp%3E%5Btex%5D%20%5Cfrac%7Bx-3%28x%2B4%29%7D%7B%28x%2B4%29%28x-4%29%7D%20%3D%5Cfrac%7Bx-3x-12%7D%7B%28x%2B4%29%28x-4%29%7D%3D%5Cfrac%7B-2x-12%7D%7B%28x%2B4%29%28x-4%29%7D%20%3D%5Cfrac%7B-2%28x%2B6%29%7D%7B%28x%2B4%29%28x-4%29%7D%20%20)
Conclusion:
In factored form the simplified expression 
In expanded form the simplified expression 
Can you please show the line plot or send a picture through my profile. I may be able to help you then.
First you would have to convert , so 12 inches = 1 foot . So do 12 X 16= 192inches, then subtract 192-6=186inches should be the difference IN INCHES. If you need it in feet divide 186 by 12 which should give you 15.5feet
This would be it i guess??