Need i havent done this since 2015 : // lolz

21. In a parallelogram, opposite angles are equal and adjacent angles are supplementary (add to 180°).
  m∠R = m∠P = 180° -m∠Q
  m∠Q = 107°
  m∠P = 73°

25. If you draw any diagonal, it divides the figure into two congruent triangles (by the SSS postulate). Corresponding angles are congruent, so the diagonal is a transversal between parallel lines. Thus opposite sides are parallel and the figure is a parallelogram.

27. Opposite sides are equal, and the diagonals bisect each other. Your four equations are
  2w+4 = 5w-6 . . . . w = 10/3
  12 = 3x-3 . . . . . . . x = 5
  6y = 4y+6 . . . . . . . y = 3
  27 = (5/4)z +2 . . . z = 20