the answer is 30
Step-by-step explanation:
it is very hard but,i will you how i got the answer
if you know the inscribed angle which is the angle made by the chords you will that there is special case for the diameter as it divides the circle into two halves each with 180° arc angle
you know that the inscribed angle is half the angle cirumcribed by the same arc
now lets begin to solve the problem
since BAC has an angle of 60
its arc BAC is 120 degrees
since the Arc BCD is 180 degrees as the the diameter BD divides the circle
now the remainder arc CD will be 60
since there angle DBC is an inscribed angle and circumscribe the arc DC then the angle DBC is 30
