Last one for today...help me simplify a rational expression

1/3 - x/9   is what I find.....but I do not see that option....

Easiest way to do this is to factor top/bottom  separately

9 - x^2  =  (3 - x) ( 3 + x)  

9x + 27  =  9 ( x + 3)

So we have

(3 - x)  ( 3 + x)                     (3 - x) ( x + 3)                (3 - x)

____________        =       _____________   =       ________

9 ( x + 3)                             9 (x + 3)                            9