1. The problem states that for the function $f$, $f(3x) = x - 6$ for all values of $x$. We need to find $f(6)$. 2. To find $f(6)$, notice that $6 = 3 imes 2$, so we can set $3x = 6$ which gives $x = 2$. 3. Substitute $x = 2$ into the given equation: $$f(3 imes 2) = f(6) = 2 - 6$$ 4. Simplify the right side: $$f(6) = -4$$ 5. Therefore, the value of $f(6)$ is $-4$. Final answer: B. -4