Given that AOB forms a line segment we can conclude that ∠XOB and ∠AOX are supplementary angles. By the definition of supplementary angles we know that the sum of their measures is 180°.
Therefore we can write the equation:
∠XOB + ∠AOX = 180°
Since it is given that ∠XOB = ∠AOX we can substitute ∠AOX with ∠XOB in the equation:
∠XOB + ∠XOB = 180°
Combining like terms we have:
2∠XOB = 180°
Now we want to solve for the measure of ∠XOB. To isolate ∠XOB we can divide both sides of the equation by 2:
(2∠XOB)/2 = 180°/2
Simplifying we get:
∠XOB = 90°
Therefore the measure of angle ∠XOB is 90°.