Addition and subtraction are called first-order operations, and multiplication and division are called second-order operations. Only when operating at the same level, do it from left to right in turn. When operating in different levels, multiply first, then divide, and then add and subtract. When there are parentheses, count the parentheses first, then the parentheses, and finally the parentheses.

1. When operating at the same level (such as multiplication and division, addition and subtraction), the calculation should be carried out from left to right.

2. When performing two-level operation, multiply first, then divide, and then add and subtract. For example: 2×4-4÷2=6, run 2×4=8 first, then run 4÷2=2, and finally calculate 8-2=6.

3. When there are brackets, count the inside of brackets first, and then count the outside of brackets; (2×4-4)÷2=2, first run 2×4=8, then run 8-4=4, and finally calculate 4÷2=2.

4. When there are multiple brackets, count the brackets first, then the brackets inside, then the braces inside, and finally the brackets outside.

5. In the mixed operation, the numbers in brackets are calculated first, and the brackets are from small to large. If there is a power, calculate the power first, and then from high to low.