Off-line calculation is a mathematical term, that is, recursive calculation, which is an operation to write out the calculation process completely, that is, calculation that is out of vertical.

When calculating at the same level, calculate 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.

If there is a power, calculate the power first.

When performing mixed operations, the numbers in parentheses are calculated first, and the parentheses are from small to large. If there is a power, calculate the power first, and then from high to low.

Recursive operation rule