Answers:
m Arc OS = 68°
m Arc SK = 112°
m ∠OCS = 68°
m ∠SCK = 112°
m ∠OCD = 68°
m ∠DOK = 112°
m ∠DCS = 136°
m ∠ODS = 68°
m ∠ODK = 180°
m ∠ORS = 34°
m ∠OKD = 68°
Just remember that when a central angle has its same intercepted arc with other central angle then they are congruent.
Inscribed angle is 1/2 the measure of its intercepted arc.
Semicircle is equal to 180°.
