In circle A, BE and FC are diameters. Find the measure of arc FC. Explanation please and no sketchy links <3 Thank you

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.

Ineed with this problem 21 show steps

3.4a=57.8 what is the the value of a