Answer
$\frac{2}{5}$
Work Step by Step
We simplify the fraction $\frac{6}{15}$ by dividing by $\frac{3}{3}$:
$\frac{6\div3}{15\div3}=\frac{2}{5}$
The fraction $\frac{2}{5}$ is in simplest form because the only common factor of the numerator and the denominator is $1$.