Addition and subtraction skills;

The writing order of addition and subtraction is the same as that of oral calculation, which is calculated from left to right in turn. Continuous addition calculation can be calculated step by step or written as longitudinal calculation. The calculation method is the same as adding two numbers. The same numbers should be aligned and added from one digit.

The continuous subtraction operation can be calculated step by step or written as vertical calculation. The calculation method is the same as subtracting two numbers. The same numbers should be aligned, starting with single digits.

The operation order of mixed addition and subtraction formula is the same as vertical writing and addition and subtraction. The addition and subtraction mixed operation can be calculated step by step when writing vertically. The method is the same as adding and subtracting two numbers. The same numbers should be aligned, starting with single digits. You can also write in a simple way, in a vertical row. First, complete the calculation of the first step, and then add and subtract the second number with the result of the first step.