1, elementary arithmetic order: when operating at the same level, it is calculated from left to right in turn; Two-stage operation, first multiply and then divide, then add and subtract.
When there are brackets, count the inside of brackets first, and then count the outside of brackets; When there are multiple brackets, count the brackets first, then the brackets inside, then the braces inside, and finally the brackets outside.
2. Multiplication is a simple operation of addition and division is a simple operation of subtraction. Subtraction and addition are reciprocal operations, and division and multiplication are reciprocal operations.
When several addends are added, the positions of addends can be exchanged at will; Or add a few addends first and then add them with other addends, and the sum remains the same. Subtracting the sum of two numbers from a number is equivalent to subtracting each addend in the sum from this number in turn.
Operation sequence of four operations:
1. If there is only addition and subtraction or only multiplication and division, it is calculated from left to right.
2. If primary operation and secondary operation exist at the same time, the secondary operation is calculated first.
3. If there are primary, secondary and tertiary operations (i.e. power, root and logarithm operations) at the same time, first calculate the tertiary operation, and then calculate the other two levels.
4. If there are brackets, count the numbers in brackets first (no matter what level, count first).
5. The third level should be counted in brackets, and then the second and first levels should be counted.