Answer:
x = 12
Step-by-step explanation:
Given congruent triangles ABD and CBD, and expressions for corresponding angles ABD and CBD, you want the value of x in the expression for angle CBD.
Congruence
Corresponding parts of congruent triangles are congruent, so we know ...
∠ABD ≅ ∠CBD
99° = (9x -9)° . . . . use the given expressions
11 = x -1 . . . . . . . . divide by 9°
12 = x . . . . . . . . add 1
The value of x is 12.
