Answer:
30°
Step-by-step explanation:
A dilatation does not change the size of the angles in the triangles only the length of the sides.
ΔABC and ΔXYZ are therefore similar and corresponding angles are congruent, hence
∠X = ∠A = 50°
∠Y = ∠B = 100°
The sum of the 3 angles in the triangle = 180°, thus
∠Z = 180° - (50 + 100)° = 180° - 150° = 30°
