To add the fractions \(-\frac{8}{15}\) and \(\frac{4}{15}\), you can simply combine the numerators since they have the same denominator:
\[ -\frac{8}{15} + \frac{4}{15} = \frac{-8 + 4}{15} = \frac{-4}{15} \]
So the answer is:
\(-\frac{4}{15}\)
This matches the response \(-\frac{4}{15}\).