$x^2 + 20x + a = 0$
$\frac{x_1}{x_2} = \frac{7}{3}$
$x_1 = \frac{7}{3}x_2$
$x_1 + x_2 = -b$
$\frac{7}{3}x_2 + x_2 = -20$
$\frac{10}{3}x_2 = -20$
$x_2 = -20 : \frac{10}{3}$
$x_2 = -20 * \frac{3}{10}$
$x_2 = -2 * 3$
$x_2 = -6$
$x_1 = \frac{7}{3}x_2 = \frac{7}{3} * (-6) = 7 * (-2) = -14$
$x_1x_2 = c = a$
a = −14 * (−6)
a = 84
Ответ: a = 84; $x_1 = -14; x_2 = -6$.