18 or 3 * 6 because to find out how many possible contengencys you muktiplyy the factors.
C.AAS
Because vertical angles are congruent.
I believe it is 83 because a straight line is 180 degrees
A + b + c = 72
a = b - 1
c = b + 1
(b - 1) + b + (b + 1) = 72
Simplify
3b = 72
b = 24
a = 24 - 1
a = 23