When you add fractions with the same denominator, use the rule shown below:
b/a + c/a = (b+c)/a , a≠0. (subtraction: b/a - c/a = (b-c)/a)
Here, a = x-4, b = x, c = x-3 Therefore,
x/(x-4) + (x-3)/(x-4) = {x + (x-3)}/(x-4) = (x+x-3)/(x-4) = (2x-3)/(x-4)
The answer is: (2x-3)/(x-4)*
* the improper form: (2x-3)/(x-4)=(2x-8+5)/(x-4)={2(x-4)+5}/(x-4)=2(x-4)/(x-4) + 5/(x-4)=2 and 5/(x-4)