I guess you just have to use common sense and go one question at a time. For example, if a question that requires you to use simultaneous equations and is only worth 2 marks, then only the answers of the two variables are required. But if was worth say 3 or 4 marks, then you need to show working. That doesnt mean you cant use your calculator to aid you with your working, although you dont need to write down the calculator steps because the assessors know that every kid is using them. You should really familiarise yourself with the assessment reports and really get to know which type of questions require which type of working. You should get to the point where you automatically know how to set out an answer for each question without thinking, because in further, the same questions come up.