9514 1404 393
Answer:
x = 16
Step-by-step explanation:
The angle bisector divides the sides proportionally.
(x -4)/9 = x/12
4(x -4) = 3x . . . . . . . multiply by 36
x = 16 . . . . . . . . . . . . add 16-3x to both sides, simplify
