I have figured that 4 is the common denominator ie (x +4)(x-4)...
When the factors of the denominators are x + 4, x - 4, x + 1, how are you getting a common denominator of just the number "4"?
...but when I get into the subtraction of this...
What are you subtracting?
To learn how to factor quadratics, try here
. To learn how to convert rational expressions (that is, polynomial fractions) to common denominators and then how to add and subtract them, try here
Then please attempt the exercise, starting from the first step, being the factorization of the denominators:
. . . . .
all of your steps. Thank you!