[tex]\displaystyle\bf\\\frac{4}{\sqrt{12}}+\frac{20}{\sqrt{75}}=\\\\\\=\frac{4}{\sqrt{4\times3}}+\frac{20}{\sqrt{25\times3}}=\\\\\\=\frac{4}{2\sqrt{3}}+\frac{20}{5\sqrt{3}}=\\\\\\=\frac{2}{\sqrt{3}}+\frac{4}{\sqrt{3}}=\\\\\\=\frac{2+4}{\sqrt{3}}=\frac{6}{\sqrt{3}}=\frac{6\sqrt{3}}{3}=\boxed{\bf2\sqrt{3}}[/tex]
