Explanation:
Isoceles triangle.
It is a isoceles triangle since we know that one triangle angle measure is 80 we can solve the rest.
Since line AB and CD is parallel and line AC is the transversal, Angle A measure is 50 via the alternate interior angle postulate.
We can then using the triangle interior theorem to find the third angle.
80+50+x=180
130+x=180
x=50
So the third angle measure is 50.
Using the definition of a isoceles triangle, the triangle has two congruent measures so it is a isoceles triangle.