The bromide shown is treated with $\mathrm{KCN}$ in aqueous ethanol and the product is then boiled with dilute $\mathrm{HCl}$. Which structure is the final organic product?

KCN gives the nitrile (3-methylbutanenitrile, one carbon more than the bromide) by SN2 at the primary carbon. Complete acid hydrolysis converts the cyano group to a carboxylic acid: 3-methylbutanoic acid. The amide is the partial hydrolysis product; 2-methylpropanoic acid would need loss of a carbon.