Given:
Given that the line AB is parallel to CD.
The measure of ∠ABO is 50°
The measure of ∠CDO is 30°
We need to determine the value of x.
Value of x:
Let us draw a line through O, parallel to both AB and CD.
By alternate interior angles, we have;


and also, we have;


Thus, the measure of ∠BOC = ∠1 + ∠2
Substituting the values, we have;


Thus, the value of x is 80°