a)
\frac{1}{\sqrt[3]{3}}=\frac{\sqrt[3]{3^2}}{\sqrt[3]{3*3^2}}=\frac{\sqrt[3]{3^2}}{3}
b)
\frac{5}{2\sqrt[3]{7}}=\frac{5\sqrt[3]{7^2}}{2\sqrt[3]{7*7^2}}=\frac{5\sqrt[3]{7^2}}{14}
c)
\frac{3}{\sqrt[3]{4}}=\frac{3*\sqrt[3]{2}}{\sqrt[3]{2^2}*\sqrt[3]{2}}=\frac{3\sqrt[3]{2}}{2}
d)
\frac{-2}{\sqrt[3]{25}}=\frac{-2*\sqrt[3]{5}}{\sqrt[3]{5^2}*\sqrt[3]{5}}}=\frac{-2\sqrt[3]{5}}{5}