A tangent BE is drawn at B to a circle ABCD. AB is a chord such that the angle ABF = 50 degrees. Find the angle ACB.

Here's how to find the values of $x$ and $y$:

Step 1: Find the value of $y$.
The angle between a tangent and a chord through the point of contact is equal to the angle in the alternate segment. This is the Alternate Segment Theorem.
Here, $\overline{BE}$ is the tangent at $B$, and $\overline{AB}$ is a chord.
The angle $\angle ABF = 50^\circ$ is the angle between the tangent $\overline{BE}$ and the chord $\overline{AB}$.
The angle in the alternate segment subtended by chord $\overline{AB}$ is $\angle ACB$.
Therefore, by the Alternate Segment Theorem:

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