How to solve?
show work as well

First, factor the denominator.  The factors are (r+8)(r-6).

Next, Use synth. div. to determine whether either -8 or 6 is a solution of the numerator.  For example:
     
6   /     3         3       -168
                     18        126   
     
           3        21        - 42   There's a remainder, so 6 is NOT a root.

Determine whether or not -8 is a root of the numerator.  If it is, then (x+8) is a factor of both numerator and denominator of the original fraction, and this can be cancelled (but note that r can NOT = -8).