To evaluate the expression \( x - \frac{y}{3} \) when \( x = 9 \) and \( y = 6 \), we first substitute the values of \( x \) and \( y \) into the expression:
\[ x - \frac{y}{3} = 9 - \frac{6}{3} \]
Now, calculate \( \frac{6}{3} \):
\[ \frac{6}{3} = 2 \]
Now, substitute this back into the expression:
\[ 9 - 2 = 7 \]
Thus, the value of the expression when \( x = 9 \) and \( y = 6 \) is \( \boxed{7} \).
It seems that the options provided do not include 7, so if this is part of a multiple choice question, please double check the options or the expression itself. The correct evaluation is indeed 7.