Answer:
a. 156°
Step-by-step explanation:
The marked angle at P is the average of the arcs intercepted:
((13x)° + (5x+10)°)/2 = (10x -7)°
(18x +10)/2 = 10x -7 . . . . simplify a bit
9x +5 = 10x -7 . . . . . . . . simplify more
9x +12 = 10x . . . . . . . . . . add 7
12 = x . . . . . . . . . . . . . . . . subtract 9x
Now, use this value to find (13x)°.
13x° = 13(12)° = 156° . . . measure of arc DC
