Answer:
triangle ABD is a equilateral triangle.
so each angle is 60°
<ADB=60°
<BAD=60°
again
we have
CD is perpendicular to AD[tangent on the arc is perpendicular to the radius]
:. ADC=90°
°
again
In triangle ADC
<A+<B+<C=180°[sum of a interior angle of a traingle is 180°]
60°+90°+x=180°
x=180°-150°
x=30°
is a right answer.