Evaluate if it is convergent!

a) $\displaystyle\sum_{n=1}^{\infty}{\frac{{2^n}+{3^n}}{5^n}}$

b) $\displaystyle\sum_{n=1}^{\infty}{\frac{7^{n-1}}{3^n}}$

c) $\displaystyle\sum_{n=1}^{\infty}{\frac{n}{\sqrt[3]{n^2}}}$