To simplify the expression \( \frac{1}{5}(5s - 15) \), you can distribute \(\frac{1}{5}\) to each term inside the parentheses:
\[ \frac{1}{5}(5s) - \frac{1}{5}(15) \]
Calculating each term gives:
\[ s - 3 \]
So, the simplified expression is:
\[ s - 3 \]