Picture relating to the question can be found in the picture attached below.
Answer:
Angle DCA = Angle CAB
Angle A + Angle B + Angle C = 180°
18 + 3x + 3x = 180
27°
Explanation:
For 1:
Angle DCA = Angle CAB (Alternate angles are equal)
Angle DCA = 18°, Hence, CAB = 18°
2)
Angle A + Angle B + Angle C = 180° (sum of interior angles in a triangle)
3.)
Angle A = 18°
Angle B = 3x
Angle C = 3x
18° + 3x + 3x = 180°
4.)
18 + 3x + 3x = 180
18 + 6x = 180
6x = 180 - 18
6x = 162
x = 162 / 6
x = 27°