1) The way to evaluate that Absolute Value expression is to remove the absolute value bars this way, considering this to be a function
Consider x is between [3,9]
[tex]\begin{gathered} ---- \\ 3\leq x\leq9 \\ f(x)=x-3+-(x-9) \\ f(x)=x-3-x+9 \\ f(x)=6 \end{gathered}[/tex]Then we can rewrite that absolute value function, considering that all whole values for the first absolute bar will be 0 or positive, and at the same time all the values will be lesser than 9 or equal to zero.
2) Thus the answer is:
[tex]f(x)=x-3+-(x-9)[/tex]