Polygon Q is a scaled copy of polygon P using a scale factor of 1/2 polygon Q's area is what fraction of polygon P's area

I dont understand this, can someone help explain?

In the figure below, ∠dec ≅ ∠dce, ∠b ≅ ∠f, and segment df is congruent to segment bd. point c is the point of intersection between segment ag and segment bd, while point e is the point of intersection between segment ag and segment df. the figure shows a polygon comprised of three triangles, abc, dec, and gfe. prove δabc ≅ δgfe.

Which geometric principle is used to justify the construction below?

Matt had 5 library books. he checked out 1 additional book every week without retuening any books. whats the matching equation