Question 107649
Assume you mean:

{{{6/((x^2-4))}}} - {{{5/((x+2))}}}
-------------------
{{{7/((x^2-4))}}} - {{{4/((x-2))}}}
:
Note that (x^2 - 4) can be factored to (x+2)(x-2) 
That will the common denominator for both the numerator & denominator fractions.
:
{{{(6 - 5(x-2))/((x-2)(x+2))}}}     
------------- =  
{{{(7 - 4(x+2))/((x+2)(x-2))}}}     
:
:
Multiply what's inside the brackets
{{{(6 - 5x + 10)/((x-2)(x+2))}}}
----------------- =
{{{(7 - 4x - 8)/((x+2)(x-2))}}}
:
:
{{{(16 - 5x)/((x-2)(x+2))}}}
-----------------  =
{{{(-1 - 4x)/((x+2)(x-2))}}}
:
:
Invert the dividing fraction and multiply:
{{{(16 - 5x)/((x-2)(x+2))}}} * {{{((x+2)(x-2))/(-1 - 4x)}}}
:

Cancel (x+2)(x-2) and you have:
{{{(16-5x)/(-1 - 4x)}}}
:
Did this help you? Any questions?