Explanation:
Top dashed box:
AC is congruent to itself by: reflexive property of congruence
Bottom left dashed box:
Angles DAC & BCA are congruent, and angles ACD and BAC are congruent by: alternate interior angles
Bottom middle dashed box:
Triangles ACD and CAB are congruent by: ASA
Bottom right dashed box:
Segments AB and CD are congruent, and segments AD and BC are congruent by: CPCTC