Question

AB is the diameter of a circle, centre O.

D is a point on the circumference of the circle. Angle BAD is 68º.
Calculate the size of the shaded angle ABD.

Answer 1

Explanation:

to add to the other (correct) answer :

the sum of all angles in a triangle is always 180°.

and so, as the angle at D must be 90°, the angle at A is 68°, we get

180 = angle A + angle B + angle D =

= 68 + angle B + 90 = 158 + angle B

angle B = 180 - 158 = 22°

Answer 2

Check the picture below.