X with 2,4 DNPH (Brady's reagent) is used to show the presence of an aldehyde or ketone. X also reduces Copper ions (Fehling's) meaning it has to be an aldehyde and not a ketone as ketones are not readily oxidisable. A positive Brady's test will form a yellow, orange or red precipitate. A yellow precipitate indicates an aliphatic compound whereas a red one indicates an aromatic compound (i.e. a benzene ring). As Brady's reagent caused a red precipitate and we know it is an aldehyde, we can assume it is a structure like Benzaldehyde (i.e. aldehyde with aromatic compound).