When acetaldehyde is heated with Fehling solution, it gives a red precipitate, oxidation state of copper in the red ppt is +x, the value of x is

Fehlings solution is a tartaric acid complex of cupric ions. When acetaldehyde is heated with Fehling's solution, it gives a red precipitate of Cu₂O.
${\mathrm{CH}}_3\mathrm{CHO}+\underset{\text{Fehling solution }}{\underbrace{2{\mathrm{Cu}}^{+2}+5{\mathrm{OH}}^{-}}}\stackrel{∆}{\to }{\mathrm{CH}}_3{\mathrm{COO}}^{-}+\underset{\text{ red ppt. }}{{\mathrm{Cu}}_2\mathrm{O}}+3{\mathrm{H}}_2\mathrm{O}$
Acetaldehyde is oxidized to acetate ion and cupric ions are reduced to cuprous oxide.

Oxidation state of Cu in Cu₂O is +1.