If the problem isn’t calc but pre-calc, you might think of doing some self-tutoring to bulk up your core math skills. There are going to be other requirements (Econ, statistics, any finance) for a business program that will be very challenging if you’ve got a shaky math foundation. The most basic marketing concepts (pricing, promotion, distribution) are going to require math and that’s before you get to the current stuff (big data, algorithms, data mining).