Answer:
27.5
Step-by-step explanation:
<DAC is an inscribed angle that subtends a half circle, so m<DAC = 90°.
Triangle DAC is a right triangle.
CD = 30
AD = 12
(AC)² + (AD)² = (CD)²
(AC)² + 144 = 900
AC = √756
AC = 27.5
