Recursive calculation method is a calculation method in mathematics, which is used to solve formulas in elementary arithmetic. The steps of recursive calculation are as follows:

1, from left to right, count the contents in brackets first.

2. Calculate multiplication and division.

3. Finally, add and subtract. According to this order, the accuracy of the calculation results can be guaranteed. In the calculation process, an equal sign can be used to represent the calculation process of each step. Such an equation is called a recursive equation.