Ca final costing help

Hi my frnds, i have attempted my final exams for more than thrice and everytime i get low score only in costing and sfm bcos of which my grp is not getting cleared . I have worked out all pm problems and also scanners and also book problems like more than thrice for everyexam but i couldnt find out where i went wrong. i got ex in isca and law for may16 exam, So pls help me out guys where im going wrong and help me with upcoming exams . I would be so grateful and i have asked for copy of my cost paper.