Problems and exercisesMalonic and acetoacetic syntheses

Propose a synthesis of 2-methylpentanoic acid from diethyl malonate, and one of 2-hexanone from ethyl acetoacetate.

Which product is obtained by treating diethyl malonate with 2 eq. of NaOEt and 1,3-dibromopropane, and then with hot H₃O⁺?

Why do substituted malonic acids and β-keto acids decarboxylate on heating, whereas simple carboxylic acids do not?