The answer is D. 98
A quadrilateral ABCD is cyclic if and only if its opposite
angles are supplementary.
A and C are opposite angles, so they are supplementary
m∠A + m∠C = 180°
9x-1 + 64 = 180
9x+63 = 180
9x = 117
x = 13°
m∠B = 6x+4 = 6(13)+4 = 82°
B and D are opposite angles, so they are supplementary
m∠B + m∠D = 180°
82° + m∠D = 180°
m∠D = 98°
