Answer:
50°
Explanation:
The two red dashes indicate that the side lengths are the same. Since they are the same length, they are going to make the same angle with the third side. Since we already know that one of the angles is 80°, and a triangle has 180°, we can conclude that the other two angles add up to 100°.
Since there are two angles, and they are equal, we can do;
100°/2 = 50°.
This is the value of x.