The value of x = 137.
You now have a cyclic quadrilateral. That is a four-sided shape whose angle vertices meet the circumference of a circle.
The total of opposing angles equals 180 degrees.
Givens
1 degree equals 43 degrees
x
The sum of x and 1 equals 180 degrees.
Solution
x + 43 = 180
Take 43 off both sides.
Combine x + 43-43 = 180-43
x = 137