Answer:
C = 100 degrees
B = 70 degrees
Step-by-step explanation:
OPPOSITE ANGLES OF A CYCLIC QUADRILATERAL ARE SUPPLEMENTARY, WHENEVER YOU ADD THEM THEY SHOULD GIVE YOU 180 DEGREES.
SOLUTION
A + C = 180
80 + C = 180
C = 100
D + B = 180
110 + B = 180
B = 70
