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Work Shown:
Refer to the diagram below. I've added a line segment and two variables y and z. This forms two isosceles triangles.
The central angle 56 degrees subtends the same arc as the inscribed angle y. By the inscribed angle theorem, this means y = 56/2 = 28. The inscribed angle is always half of the central angle (when both angles subtend the same arc).
Focus on the smaller isosceles triangle that has angles 56, z and z. Those three angles add to 180
z+z+56 = 180
2z+56 = 180
2z = 180-56
2z = 124
z = 124/2
z = 62
Now focus on the larger isosceles triangle (angles y = 28, x+z and x+z)
We'll use the same trick as before.
(x+z)+(x+z)+(y) = 180
(x+62)+(x+62)+(28) = 180 ... plug in z = 62 and y = 28
2x+152 = 180
2x = 180-152
2x = 28
x = 28/2
x = 14
