Your answer is incorrect and it's practically incomprehensible. The subject of your sentence is 学经济的人 （people studying economics, "study-economics-people") and your predicate is 多 (many). So putting it altogether:

学经济的人(很)多。 (positive) or 学经济的人不多。 (negative answer).

Your answer is incorrect. The subject of your sentence is 学经济的人 （people studying economics, "study-economics-people") and your predicate is 多 (many). So putting it altogether:

学经济的人(很)多。 (positive) or 学经济的人不多。 (negative answer).