I really dislike these stupid algebra problems pretending to be geometry. To the question writer: the measures are equal, the angles are congruent.
The two angles are equal measure so
4x + 3 = 12x
3 = 8x
x = 3/8
KIH = (12 (3/8))° = 9/2 = 4.5°
Answer: 4.5°
