x° = 100°
Solution:
The reference image to the answer is attached below.
Given ∠AOC = 100°, ∠BOD = x°
To find the value of x°:
∠AOC and ∠BOD are vertically opposite angles.
Vertical angle theorem:
If two lines are intersecting each other, then vertically opposite angles are congruent.
In the given image line AB and line CD are intersecting angles.
They intersect at point O.
By vertical angle theorem, they are congruent.
⇒ ∠AOC ≅ ∠BOD
⇒ m∠BOD = 100°
⇒ x° = 100°
Hence the value of x° is 100°.