Replace y in the first equation by "3x", based on the second equation. You will get 3x = x^2 + 6x + 9, x^2 + 3x + 9 = 0, which has no real solutions, since the discriminant d = b^2 - 4ac = 3^2 - 4*9 = 9 - 36 = -27 is negative. The equation has two solutions in complex numbers= .