Answer:
x = 129°
Step-by-step explanation:
Since AB ~ BC then Δ ABC is isosceles and the 2 base angles are congruent.
∠ ACB = [tex]\frac{180-78}{2}[/tex] = [tex]\frac{102}{2}[/tex] = 51°
∠ ACB and x are adjacent angles and are supplementary, sum to 180°, then
x = 180 °- 51° = 129°
