Solution :
In triangle PQO,
Given, DE || OQ
By Basic proportionality theorem, we have
\(PE\over EQ\) = \(PD\over DO\) ……..(1)
In triangle POR,
Given, DF || OR
By Basic proportionality theorem, we have
\(PD\over DO\) = \(PF\over FR\) ……..(2)
From (1) and (2), we obtain that
\(PE\over EQ\) = \(PF\over FR\)
Hence, By converse of basic proportionality theorem, we have
EF || QR