PLEASE HELP
What is the measure of AC?
A. 42°
B. 132°
C. 138°
D. 48°

Answer:
C. 138°
Step-by-step explanation:
< ABC = 1/2 ( ac + de)
90 = 1/2 (ac +42)
multiply each side by 2
2*90 = 2*12/ (ac+42)
180 = ac+42
subtract 42 from each side
180-42 = ac
138 = ac