1. Q is the midpoint of PR 1. Given 2. PQ = QR 2. Definition of midpoint of a segment 3. R is the midpoint o QS 3. Given 4. QR = RS 4. Definition of midpoint of a segment 5. PQ + QR = QR + RS 5. Addition property of equality 6. PR = QS 6. Segment addition postulate
