Answer:
See attached picture.
Step-by-step explanation:
Hello.
In this case, since the synthesis of amides via anhydride requires its reaction with the N-radical primary amine, as it is required to yield N-methylpropanamide, the reactants must be propanoic anhydride and methylamine in order to yield the aforementioned amide as well as propanoic acid as a side product.
This reaction is shown on the attached picture.
Best regards.