To solve the inequality \( 9w < 108 \), we can divide both sides by \( 9 \):
\[ w < \frac{108}{9} \]
Calculating the right side gives:
\[ w < 12 \]
So, the solution to the inequality \( 9w < 108 \) is:
\[ w < 12 \]
Thus, the correct answer is \( w < 12 \).