No, NOT all persons can understand math. Some people are retarded, some people are stupid, some people are average, some people are smart, some people are geniuses.
Pretty much everyone, even some animals, can grasp 2 + 2 = 4. How far above that point they can grasp is a function of mental capability and dedication. Not everyone has the mental capacity to grasp differential equations but that is a matter of the individual, not race or any other human invented division.