[tex]\frac{\sqrt{2}-1}{\sqrt2}+\frac{\sqrt3-\sqrt2}{\sqrt6}+\frac{\sqrt4-\sqrt3}{\sqrt{12}}=\\
\frac{\sqrt2-1}{\sqrt2\cdot1}+\frac{\sqrt3-\sqrt{2}}{\sqrt3\cdot\sqrt2}+\frac{\sqrt4-\sqrt3}{\sqrt4\cdot \sqrt3}=\\
1-\frac{1}{\sqrt2}+\frac{1}{\sqrt2}-\frac{1}{\sqrt3}+\frac{1}{\sqrt3}-\frac{1}{\sqrt4}=\\
1-\frac{1}{\sqrt4}=\\
1-\frac{1}{2}=\frac{1}{2}\\
\\
\frac{x}{2\sqrt3}=\frac{8\sqrt3}{x}\\
x^2=8\sqrt3\cdot2\sqrt3\\
x^2=16\cdot3\\
|x|=4\sqrt3\\
S:x\in \{4\sqrt3},-4\sqrt3\}[/tex]