In a cyclic quadrilateral we know that the exterior angle is equal to the interior opposite angle
So we get
∠BAD=∠DCF=75o
It can be written as
∠DCF=x=75o
We get x=75o
We know that the opposite angles of a cyclic quadrilateral is 180o
So we get
∠DCF+∠DEF=180o
By substituting the values
75o+∠DEF=180o
On further calculation
∠DEF=180o−75o
By subtraction
∠DEF=y=105o
Therefore, the value of x and y is 75o and 105o.