So what they do (or at least most exam boards) is tally up the marks and make it out of the total marks available for all course assessments/ papers. If you get a B in coursework but A in exams, you will definitely pass with high-grade A marks. If you get a C in the coursework but As, you're likely to get B to low A. Really depends how many marks you get from the exam/ written paper(s). Good luck!