Basic Math, yes, but it isn't even about the Math. Although it would bode well, the correct answer isn't the point; I'm more interested in the response/approach. For example, a response such as "

I was always bad at Math or I'm not a Math person" is

but one like "

I think it might be this [insert value] followed by what's the correct answer though" would be better. It's more about getting a glimpse into one's character such as willingness to learn new things or being able to admit you don't know something rather than using a cheap excuse.