Write the property of alternate angles formed by two parallel lines and a transversal?

They are congruent

Step-by-step explanation:

If two angles are formed by parallel lines and a transversal, the angles are congruent. This is due to the angles being supplimentary (equal to 180 degrees). If your angle is equal to 80 degrees, the other side would have to equal 100. Which would cary over the the other line making the transversal angle 80 degrees.

When two or more lines are cut by a transversal, the angles which occupy the same relative position are called corresponding angles. When the lines are parallel, the corresponding angles are congruent ... If two parallel lines are cut by a transversal, then the alternate interior angles formed are congruent.