a.
$A=(\frac{2\sqrt{x}}{\sqrt{x}+3}+\frac{\sqrt{x}}{\sqrt{x}-3}+\frac{3x+3}{9-x}):(\frac{\sqrt{x}-1}{\sqrt{x}-3}-\frac{1}{2})$
$A=\frac{2\sqrt{x}( \sqrt{x}-3)+\sqrt{x}( \sqrt{x}+3)-(3x+3)}{\left ( \sqrt{x}-3 \right )\left ( \sqrt{x}+3 \right )}:\frac{2\sqrt{x}-2-\sqrt{x}+3}{2(\sqrt{x}-3)}$
$A=\frac{-3( \sqrt{x}+1)}{\left ( \sqrt{x}-3 \right )\left ( \sqrt{x}+3 \right )}. \frac{2(\sqrt{x}-3)}{\sqrt{x}+1}$
$A=\frac{-6}{\sqrt{x}+3}$