To simplify the expression \( 3(3 + 5w) \), we can distribute the 3 across the terms inside the parentheses.
\[ 3(3 + 5w) = 3 \cdot 3 + 3 \cdot 5w \]
Calculating each part:
\[ 3 \cdot 3 = 9 \] \[ 3 \cdot 5w = 15w \]
Putting it all together:
\[ 3(3 + 5w) = 9 + 15w \]
Thus, the simplified expression is:
\[ \boxed{9 + 15w} \]