The value of x in the diagram is 45°
Vertical angles are pairs of non-adjacent angles formed by the intersection of two lines.
They are opposite each other and have equal measures. Vertical angles share a common vertex but have no common sides.
In the diagram, angle x and angle 25 and angle 30 are vertical angles
angle x = angle AFE + angle AEC
angle x = 25 + 20
angle x = 45°
Therefore angle x is 45 °. This is because they are vertically opposite angles and they are equal.