Умножим обе части уравнения на 15:
$$5(x^2+2) - 3(12x-8) = -2 * 15$$
$$5x^2 + 10 - 36x + 24 = -30$$
$$5x^2 - 36x + 34 = -30$$
$$5x^2 - 36x + 64 = 0$$
$$D = b^2 - 4ac = (-36)^2 - 4 * 5 * 64 = 1296 - 1280 = 16$$
$$x_{1,2} = \frac{-b \pm \sqrt{D}}{2a} = \frac{36 \pm \sqrt{16}}{2 * 5} = \frac{36 \pm 4}{10}$$
$$x_1 = \frac{36 + 4}{10} = \frac{40}{10} = 4$$
$$x_2 = \frac{36 - 4}{10} = \frac{32}{10} = \frac{16}{5}$$
Ответ: $$x_1 = 4$$, $$x_2 = \frac{16}{5}$$