In the triangle ACD the angles must sum to 180°, so:
x2+154+15x=180,
x2+15x=180-154=26,
x2+15x+225/4=26+225/4, completing the square,
(x+15/2)2=(104+225)/4=329/4,
x+15/2=√329/2,
x=√329/2-15/2=1.5692° approx.
m∠A=x2=2.4623° approx.
(m∠D=15x=23.5377° approx, and 2.4623+154+23.5377=180.)