My problem is

compute and simplify the difference quotient f(x+h)-f(x)/h h is not = 0
f(x)=7x-9
answer is 7

What happens if you replace x by x + h? Only the termm 7 x changes, right? It changes by 7 h. So, f(x+h) - f(x) must be 7 h and if you divide this by h you get 7.

To compute and simplify the difference quotient for the function f(x) = 7x - 9, you need to substitute the given expression into the formula (f(x+h) - f(x))/h, and then simplify the expression.

Step 1: Substitute the function into the formula:
(f(x+h) - f(x))/h = [(7(x+h) - 9) - (7x - 9)]/h

Step 2: Simplify the numerator:
= [7x + 7h - 9 - 7x + 9]/h
= (7x - 7x + 7h - 9 + 9)/h
= 7h/h

Step 3: Simplify the expression:
= 7

Therefore, the simplified difference quotient is 7.