$$\left. \begin{array} { l } { b } \\ { \frac { 5 + 2 \sqrt { 3 } } { 7 + 4 \sqrt { 3 } } = a - b \sqrt { 3 } } \end{array} \right.$$
$a=\sqrt{3}c+11-6\sqrt{3}$
$b=c$
