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$\frac{1}{ \sqrt{3}+2 }+ \frac{13}{4+ \sqrt{3}}- \frac{11}{ 1-2\sqrt{3} }= \\ \\ =\frac{1(\sqrt{3}-2 )}{ (\sqrt{3}+2)(\sqrt{3}-2 ) }+ \frac{13(4- \sqrt{3})}{(4+ \sqrt{3})(4- \sqrt{3})}- \frac{11(1+2 \sqrt{3})}{ (1-2\sqrt{3})(1+2 \sqrt{3}) }= \\ \\ \frac{1(\sqrt{3}-2 )}{ 3-4 }+ \frac{13(4- \sqrt{3})}{16-3}- \frac{11(1+2 \sqrt{3})}{ 1-12}=\frac{1(\sqrt{3}-2 )}{ -1 }+ \frac{13(4- \sqrt{3})}{13}- \frac{11(1+2 \sqrt{3})}{ -11}= \\ \\ =-( \sqrt{3}-2 )+4-\sqrt{3}+1+2\sqrt{3}=$ $=- \sqrt{3}+2 +4-\sqrt{3}+1+2\sqrt{3}=7$