From the given, it is obvious that angle I is the opposite angle of angle D. This means that the sum of the measures of these two should be equal to 180°.
If we are to look closely to the figure, angle I intercepted the arc BDR. Also, the angle D intercepted arc BIR. The sum of the measures these two arcs is 360°. Hence, the sum of the measures of the angles intercepting these arcs is 180°.
m∠I + m∠D = 180°
117° + m∠D = 180°
The measure of angle D is 63°.
Answer: 63°
