Draw the two triangles so the two triangles share point C. It should look like a bowtie. (1) AB is parallel to DE Given (2) Angle A = Angle D If two parallel lines are cut by a transversal, alternate interior angles are equal. Angle B = Angle E (3) Angle BCA = Angle DCE Vertical angles are equal. (4) Triangle BAC is similar to Triangle DEC If 3 angles in one triangle are equal to three angles in another triangle, the triangles are similar. (5) AB/DE = AC/EC If two triangles are similar, corresponding sides are proportional. Hope this helps.