R, S, Q and P are the midpoints of OC, CB, BA and OA respectively. OR = a, CS = b and OP = c
А
Show that RS is parallel to PQ

See below.

Step-by-step explanation:

Draw segment OB.

In triangle OBC, points R and S are the midpoints of sides OC and BC, respectively. That makes RS parallel to OB.

In triangle OBA, points P and Q are the midpoints of sides OA and BA, respectively. That makes PQ parallel to OB.

Since segments RS and PQ are parallel to segment OB, then RS and PQ are parallel to each other.

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step-by-step explanation: