Explanation:

∠ BAC = 24
∠ ACB = 90 (Angle on semicircle)
ABCD is a trapezium, so AB is parallel to CD
∠ ACD = ∠ BAC = 24 (Alternate angle)

∠ BCD = ∠ ACB + ∠ ACD = 90 + 24 = 114
ABCD is a cyclic quadrilateral because all point lies on same circle

∠ BAD + ∠ BCD = 180
∠ BAD + 114 = 180
∠ BAD = 66
∠ BAD = ∠ BAC + ∠ CAD
66 = 24 + ∠ CAD
∠ CAD = 66 − 24 = 42