RQP=ONP
Since R is the midpoint of MQ, then MR and RQ are equal.
Since R is the midpoint of MQ, then P must be the midpoint of NQ
The triangles are congruent and the trapezoid is three or those triangles.
RQR reflected is a triangle inside the trapezoid. The triangles at the left and right of the trapezoid are congruent.
Since all the triangles are the exact same, then they have the same height and same length.
So you connect them without like sliding a triangle up a little bit.
The 4 congruent triangles add up to be a parallelogram.
I don't know if this is what you learned in class or where ever you did learn it but this is my way (not where-I-learned-it-from's way).