Properties of parallelograms
0. Opposite sides are congruent (AB = DC).
,1. Opposite angels are congruent (D = B).
,2. Consecutive angles are supplementary, (A + D = 180°).
,3. If one angle is right, then all angles are right.
,4. The diagonals of a parallelogram bisect each other.
,5. Each diagonal of a parallelogram separates it into two congruent triangles.
Procedure
Consecutive angles
[tex]\begin{gathered} D+C=180 \\ C=180-D \\ C=180-72 \\ C=108 \end{gathered}[/tex]