#### Answer

$\frac{9a+4}{10}$

#### Work Step by Step

$\frac{9a}{10}+\frac{2}{5}$ $\longrightarrow$ convert to like fractions
=$\frac{9a}{10}+\frac{2\times2}{5\times2}$ $\longrightarrow$ mutiply
=$\frac{9a}{10}+\frac{4}{10}$ $\longrightarrow$ add numerators
=$\frac{9a+4}{10}$