Answer
$\frac{39}{40}$
Work Step by Step
The LCD of the original denominators, 5 and 8, is 40. Therefore, we can rewrite both fractions with a denominator of 40.
$\frac{3}{5}+\frac{3}{8}=\frac{3\times8}{5\times8}+\frac{3\times5}{8\times5}=\frac{24}{40}+\frac{15}{40}=\frac{24+15}{40}=\frac{39}{40}$
