The Corresponding Angles Postulate states that when parallel lines cross a third line, the angles created are congruent. So the first blank should be BDE=BAC and BED=BCA.
Now we know that the triangles BDE and BAC have two sets of congruent angles. Therefore, the second blank should be AA Similarity Postulate.
Finally, the last blank is Segment Addition Postulate which states that if a point Y is on segment XZ, then XY + YZ = XZ.