add

(1) Add two numbers and keep the number unchanged: if one of the added two numbers increases, the other decreases, the other increases and the other decreases.

(2) When two numbers are added, one of them remains the same. If the other number changes, this number will also change, and the change of the result is as big as the change of the addend.

(3) Add the two numbers and exchange positions to get the same number.

subtraction

(1) Subtract one number from another to keep the reduction unchanged: if the minuend increases, the result will also increase, and the result will increase as much as the minuend increases; When the minuend is reduced, the result is also reduced, and the result is also reduced by how much the minuend is.

(2) Subtract one number from another to keep the minuend unchanged: the meiosis increases, the result decreases, and the meiosis increases and the result decreases; If meiosis decreases, the results increase, and the results increase by how much meiosis decreases.

(3) Subtract one number from another and keep this number unchanged: the minuend will increase as much as it increases; As much as the minuend is reduced, the minuend will also be reduced.

The first property of addition: if two numbers are added, if they want to remain the same, when one addend decreases, the other addend needs to increase, and the amount of decrease is equal to the amount of increase.

The second property of addition: adding two numbers. If one addend is increased or decreased and the other addend remains the same, the sum is increased or decreased by an amount equal to that of the addend.

The third property of addition: the addition of two numbers If both addends are increased or decreased, their sum is also increased or decreased correspondingly, and the amount of increase or decrease is the sum of the amounts of increase or decrease of addends.

Add two addends, swap the positions of the two addends, and the sum remains the same.