Respuesta :

The sum of the opposite interior angles is equal to the exterior angle.

So,

∠CAB + ∠ACB = ∠CBD

x + 40 + 3x + 10 = 6x

4x + 50 = 6x

2x = 50

x = 25°

∠CAB = x + 40 = 25 + 40 = 65°

Hence, the answer is D.