Nancy bought a soda for $3 and $9 sandwiches, all for the same price she spent a total of $39. How much did each sandwich cost?

Any is very appreciated! (picture is provided below)not sure how to do this at all won't lie

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 type of graph would allow us to compare the median number of teeth for mammals and reptiles easily