Question

What is the measure of a

Answer 1

I guess you want the measure of angle <CAB.

The angle ABD is flat thus its amplitude is 180 degrees. Because
<ABD = <ABC + <CBD you get
<ABC = <ABD - <CBD = 180° - 122° = 58°.

In a triangle, the sum of the amplitudes of the angles is 180°. Thus
<CAB + <ABC + <ACB = 180°. You get
<CAB = 180° - <ABC - <ACB = 47°.