Can someone please help me out with this geometry problem? I've been stuck on it for almost an hour.

Answer:
The answer is [tex]x = 16[/tex]
Step-by-step explanation:
Solution:
Let we first name the Triangle as Δ ABC and ray BD as a bisector of ∠B
as shown in the figure below.
As ray BD is the bisector of angle B so, by Angle bisector theorem property we have
[tex]\frac{AB}{BC} = \frac{AD}{DC}\\[/tex]
∴ [tex]\frac{x}{12} =\frac{x-4}{9}[/tex]
∴ [tex]\frac{x}{4} = \frac{x-4}{3}[/tex]
∴ [tex]3x = 4x -16[/tex]
∴ [tex]x = 16[/tex] final answer