find the LCD and solve:

x+3 12x + 4 1 - 2x
____ + _________ = _______

3-x x squared - 9 x + 3

-(x+3)/(x-3)+(12x+4)/(x-3)(x+3) -2x/(x+3)

LCD = (x+3)(x-3) which is (x^2-9)
so

-(x+3)(x+3)/LCD +(12x+4)/LCD- 2x(x-3)/LCD

-x^2 - 6x - 9 + 12x + 4 -2x^2 + 6 x
all over LCD

(-3 x^2 + 12 x -5)/(x^2-9)
check my arithmetic