Primary operation: addition and subtraction.

Secondary operations: multiplication and division.

Operation order: multiply first, then divide, then add and subtract. If there are brackets, count them first, and then count them outside. In the same level of operation, the calculation order is from left to right.

Help understand:

If there is only addition and subtraction or only multiplication and division, count from left to right. (Calculation at the same level)

If there are both primary and secondary operations, the secondary operation is calculated first.

If there are brackets, count the numbers in brackets first (no matter what level).

About the calculation in brackets: first calculate the brackets, then the brackets and braces, and then calculate the brackets as the second level and then the first level.