Answer is x = 50 degrees
Step by step
It appears they are showing two pairs of congruent adjacent angles. One set is showing each at 40 degrees.
2 x 40 = 80.
We know the supplemental angle is 180 degrees. 180 - 80 = 100 for the second set that we are looking for.
Since x and it’s adjacent angle are congruent, or equal, we divide 100 by 2 equal parts = 50 degrees each. So x = 50 degrees.