We have to find the measure of x.
The angle x is supplementary to the an angle of the the triangle of which we don't know the measure. If we call this angle α (alpha) we can write:
As we don't know the value of alpha, we can not do more with this for now.
We also know that the sum of the measures od the interior angles of a triangle is equal to 180°, so we can write:
We can replace alpha with:
Answer: x = 143°