How To Prove Pappus's Hexagon Theorem using the triangle $\bigtriangleup{XYZ}$

Question

The problem says that if $A,B,C$ are three collinear points and $D,E,F$ also are three collinear points, and the intersections of the lines $\overline{AB},\overline{AF},\overline{BF}$ with the lines $\overline{DB},\overline{DC},\overline{EC}$ are the points $P,Q,R$ respectively, then this three points are also collinear. We have to prove this using the triangle $\bigtriangleup{XYZ}$ (but it doesn't make sense to me, please help).

Pappus Theorem Diagram