make denomenators the same
times left denomenator by (x+3)/(x+3) and right one by (x-9)/(x-9)
[tex] \frac{3(x+3)}{(x-9)(x+3)}+ \frac{5(x-9)}{(x-9)(x+3)}[/tex]=
[tex]\frac{3(x+3)+5(x-9)}{(x-9)(x+3)}[/tex]=
[tex]\frac{3x+9+5x-45}{(x-9)(x+3)}[/tex]=
[tex]\frac{8x-36}{(x-9)(x+3)}[/tex]
if expandded we get
[tex]\frac{8x-36}{x^2-6x-27}[/tex]
