Answer
Another function value of the graph of $g$ or $y=f(x)$ that is symmetric with respect to the line $x = 6$ is $f(3+6)=6$ or $f(9) = 6$,
Work Step by Step
When the graph of $g$ of an equation is symmetric with respect to the line $x = 6$, it will be same as the graph of $f$ of an equation that is symmetric with respect to the y-axis, but translated 6 units to the right.
Then, for every point $(x, y)$ on the graph of $f$, there will be a corresponding point $(x + 6, y)$ on the graph of g.
So, for a function $f$, $f(3)=6$, another function value of the graph of $g$ or $y=f(x)$ that is symmetric with respect to the line $x = 6$ is $f(3+6)=6$ or $f(9) = 6$,
