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Make sure to finish your homework before dinner.
Literal
Dinner-before [at-に] homework [object-を] finish-[make-so-ようにしなさい].
Motherly or teacher-style directive. 終える is the transitive 'to finish [something]' — paired with 宿題 here. ~ようにしなさい combines the habitual/purposive ~ようにする ('make it so that,' 'make a habit of') with the soft imperative ~なさい — 'make sure you X.' A gentle but firm instruction.