$$\left. \begin{array} { l } { x = \sqrt { \frac { 5 x } { 2 } + \frac { 1 } { 6 } } } \\ { a = 2 x - \frac { 1 } { 3 } } \end{array} \right.$$
$x = \frac{\sqrt{249} + 15}{12} \approx 2.56497782$
$a = \frac{\sqrt{249} + 13}{6} \approx 4.796622306$
