BODMAS is a useful mnemonic for remembering the arithmetic rules of precedence or order:

A quick test to see if a calculator obeys the rules of order is to enter 2+3x4: a simple calculator will evaluate the 2+3 immediately to get 5, then multiply by 4 for a result of 20. The correct answer is 14, which is arrived at by doing the 3x4 first to get 12, then adding the 2.

Where the equal priority of DM and AS may cause ambiguity, it is wise to use brackets to make the desired order of calculation clear, even if those brackets are redundant.