Translation:My mother's cake is better than ever.
I translated to English as "My mother's cake is better than ever," which was marked incorrect. Is there a reason this would not be an accepted translation?
"Meilleur, meilleure, meilleurs, meilleures" is an adjective, the comparative forms of the adjective "bon, bonne, bons, bonnes".
"Mieux" is an adverb, the comparative form of the adverb "bien".