A history book that weighs 30 N is placed on top of a literature book that weighs 10 N. If up is considered the positive direction, what is the force that

Question

The history book exerts on the literature book?

I know that the literature book would exert 30N on the history book. But the thing that is confusing me is when it says the whole positive direction...what am I supposed to do with that? Does that mean it is reversed?