Answer:
Isosceles triangle
Explanation:
Thorough explanation: Through the angles in the triangle ABC.
First, observe that angle ACD = 50 degrees (given)
Since lines AB and DE are parallel to each other,
angle BAC = angle ACD = 50 degrees (by the property of alternate angles)
It is also given that angle ABC = 80 degrees.
Since ABC is a triangle, the sum of the three angles must add up to 180 degrees.
Angle BAC + Angle ABC + Angle ACB = 180 degrees
50 + 80 + Angle ACB = 180
Angle ACB = 180 - 50 - 80
= 50 degrees
Since two of the angles, angles ACB and BAC are the same at 50 degrees, triangle ABC is an isosceles triangle. (With sides AB and BC equal)