Solution:We can see that the triangle has two equal sides. So, the triangle will have two equal opposite angles. It is an isosceles triangle.Given, an angle measures 80°.We take the measure of each of the two equal angles as x°.We know, the sum of all angles of a triangle is 180°.Therefore, by the problem
x + x + 80° = 180°
or, 2x = 180° - 80°
or, 2x = 100°
or, x = 100° ÷ 2
or, x = 50°
The value of x in the triangle is 50°.