Addition, subtraction, multiplication and division are called four operations.

Among them, addition and subtraction are called first-order operations, and multiplication and division are called second-order operations.

operation sequence

When there is only one level of operation, it is calculated from left to right;

When there are two levels of operation, multiply first and then divide, then add and subtract;

When there is a layer of brackets, count the brackets first;

When there are multiple parentheses, count the parentheses first.

If there is a square, count it first.