exam of ffa

I assume you are referring to the Revision Kits, in which case they are both ACCA approved and are both good. Ideally you should practice every question, but if your exam is tomorrow then you obviously don't really have the time to. In the exam itself it is important to watch your time. As soon as you find a question is taking too long then leave it - you can always come back to it later. Also, if you do not understand a question or you get stuck, then guess an answer :-)