Good afternoon!
[tex]\dfrac{10}{\sqrt{5}}+\sqrt{20}=\dfrac{10}{\sqrt{5}}\overbrace{\left(\times\dfrac{\sqrt{5}}{\sqrt{5}}\right)}^{\times 1}+\sqrt{\underbrace{4\times 5}_{20}}[/tex]
[tex]=\dfrac{10\sqrt{5}}{\left(\sqrt{5}\right)^2}+\sqrt{4}\times\sqrt{5}=\dfrac{10\sqrt{5}}{5}+2\sqrt{5}[/tex]
[tex]=\dfrac{\cancel{10}^2\sqrt{5}}{\cancel{5}}+2\sqrt{5}=2\sqrt{5}+2\sqrt{5}=\color{blue}\boxed{4\sqrt{5}}[/tex]
I hope to have helped u!