Question 972514
{3/(x-4)} / 1- (2/(x-4)}
That is how I understand the question.

Put the second over a common denominator, x-4.
1- (2/x-4)

[x-4-2}/x-4
x-6/x-4

We are dividing numerator and denominator each by x-4.  That can cancel.  We are left with the numerator of the numerator divided by the numerator of the denominator.

That is 3/(x-6)
If the question is different from the one I answered, such as a denominator of 1-(2/x)-4, then the answer will be different.  I interpreted it as shown above.