well, there's nothing to solve per se, however assuming you meant "rationalizing the denominator", which means namely to "get rid of that pesky radical at the bottom", then
[tex]\bf a^{\frac{ n}{ m}} \implies \sqrt[ m]{a^ n}
\qquad \qquad
\sqrt[ m]{a^ n}\implies a^{\frac{ n}{ m}}\\\\
-------------------------------[/tex]
[tex]\bf \cfrac{1}{y^{\frac{2}{5}}}\implies \cfrac{1}{\sqrt[5]{y^2}} \quad \stackrel{rationalizing~it}{\implies }\quad \cfrac{1}{\sqrt[5]{y^2}}\cdot \cfrac{\sqrt[5]{y^3}}{\sqrt[5]{y^3}}\implies \cfrac{\sqrt[5]{y^3}}{\sqrt[5]{y^2}\cdot \sqrt[5]{y^3}}
\\\\\\
\cfrac{\sqrt[5]{y^3}}{\sqrt[5]{y^2y^3}}\implies \cfrac{\sqrt[5]{y^3}}{\sqrt[5]{y^{2+3}}}\implies \cfrac{\sqrt[5]{y^3}}{\sqrt[5]{y^5}}\implies \cfrac{\sqrt[5]{y^3}}{y}[/tex]
