We have been given that the chords AB and CD are equal.
Now, we know that two equal chords subtends equal angle at the center of the circle.
The chord CD subtends and angle CPD at the center and the chord AB subtends an angle APB at the center.
Hence, from above mentioned theorem, we can say that
[tex]\angle CPD = \angle APB[/tex]
Now, we have been given that
[tex]\angle CPD =50 ^{\circ} [/tex]
[tex]\angle APB =x ^{\circ} [/tex]
Hence, we have
[tex]x=50^{\circ}[/tex]
