In ΔPQO,DE||OQ (Given)
∴PDDO=PEEQ...(i) [By using Basic Proportionality Theorem]
In ΔPOR,DF||OR (Given)
∴PDDO=PFFR...(ii) [By using Basic Proportionality Theorem]
From equation (i) and (ii), we get,
PEEQ=PFFR
So, ΔPQR,EF || QR [By converse of Basic Proportionality Theorem]