We want to find the values where the following expression is undefined:
[tex]\frac{x+9}{3-x}[/tex]
A rational expression is undefined when the denominator is equal to zero, then, the solution for the following equation is our answer:
[tex]3-x=0[/tex]
Solving for x, we have:
[tex]\begin{gathered} 3-x=0 \\ 3-x-3=-3 \\ -x=-3 \\ x=3 \end{gathered}[/tex]
The expression is undefined at x = 3. The answer is option B.
