Here's a quote from the past:

Marks are of the following three types:

M Method mark, awarded for a valid method applied to the problem. Method marks are not lost for numerical errors, algebraic slips or errors in units. However, it is not usually sufficient for a candidate just to indicate an intention of using some method or just to quote a formula; the formula or idea must be applied to the specific problem in hand, e.g. by substituting the relevant quantities into the formula. Correct application of a formula without the formula being quoted obviously earns the M mark and in some cases an M mark can be implied from a correct answer.

A Accuracy mark, awarded for a correct answer or intermediate step correctly obtained. Accuracy marks cannot be given unless the associated method mark is earned (or implied).

B Accuracy mark for a correct result or statement independent of method marks.

More details and Miss Loi's elaboration (as applied to local context) here but in a nutshell,

• M leads to A (answer mark) and you cannot get A without M i.e. your workings leading up to the answer must be correct - no A mark(s) will be awarded should you happen to obtain your answer without workings or by by luck (usually in long multi-mark questions)
• B (the other kind of answer mark) is independent of M (usually in short 1-mark questions or, say, a 3-mark question requiring 3 specific answers)

Plus, a few of the questions also steps correct but final answer wrong Dx

anyways, thanks for the solutions! i was afraid i'll fail my amaths actually.

ありがと！