Answer
The missing blanks can be found to be the following:
1. Given
2. Angles B and ECD are congruent.
3. AC is parallel to DE
4. When two lines that are parallel are cut by the same transversal, their corresponding angles are congruent.
5. AA
6. $\frac{AB}{DC} = \frac{BC}{CE}$; Reason: CSSTP
