6x / (x + 3) = [9 / (x - 3)] - [15 / (x^2 - 9)]
6x(x - 3) / (x + 3)(x - 3) = [9(x + 3) / (x + 3)(x - 3)] - [15 / (x^2 - 9)]
(6x^2 - 18x) / (x^2 - 9) = [(9x + 27) / (x^2 - 9)] - [15 / (x^2 - 9)]
6x^2 - 18x = 9x + 27 - 15
6x^2 - 18x - 9x - 12 = 0
6x^2 - 27x - 12 = 0
2x^2 - 9x - 4 = 0
2(x^2 - (9/2)x) - 4 = 0
2(x - (9/4))^2 - (81/8) - 4 = 0
2(x - (9/4))^2 = 113 / 8
(x - (9/4))^2 = 113 / 16
x - 9/4 = sqrt(113 / 16) or = -sqrt(113 / 16)
x = 9/4 + sqrt(113 / 16) or x = 9/4 - sqrt(113 / 16)