Answer:
42°
Explanation:
The two tick marks tell us that ∠CAD and ∠BAD are equivalent. This means that ∠CAD is also equivalent to 21 degrees. Since ∠CAB has been bisected (or divided in 2) to make ∠CAD and ∠BAD, it is equal to the sum of the two angles.
21° + 21° = 42°