Trying to understand practical economics..

The subjects I always struggle the most with are subjects including calculations and economy. The last final this semester is Practical Economics and Management, so naturaly I am rather confused trying to study for it. I am now trying to solve a series of problems related to technical budgeting, and it makes me rather frustrated how little I understand.. I have never had any ambitions about awesome super grades in this subject, but it would be nice to at least not fail it.. hope I can manage that at least. The plan is to study 7-9 hours a day all weekend - as I solve the problems or learn from the solutions sheet how they should be solved I write down the formulas in a way that I can actually understand - then I will try to memorize the formulas that I have written down. I think it's the best I can do... hopefully that will save me from a fail. I am worried about things I shouldn't worry about - affraid I have failed both the last two finals I did, even if I actually wrote quite a lot on them both and I can't know anything untill I get them back.. the thing is that if I somehow failed those two and I also fail this one I don't have enough credits to go study in China.. so I hope I didn't!