The calculation can be made easier by using the algorithm.

Additive commutative law

When two numbers are added, the positions of the addend are exchanged and the sum is unchanged. a+b=b+a

associative law of addition

Add three numbers, first add the first two numbers, or add the last two numbers first, and the sum remains the same. (a+b)+c=a+(b+c)

The essence of subtraction

Subtracting a number is equal to adding the reciprocal of this number. a-b=a+(-b)

Subtracting two numbers in a row is equal to subtracting the sum of these two numbers. a-b-c=a-(b+c)

Subtracting one number and adding another number equals subtracting the difference between the two numbers. a-b+c=a+(c-b)