When two numbers are added, the positions of addends are exchanged, and their sum is unchanged, that is, A+B = B+A.

2. Additive associative law

Add three numbers, first add the first two numbers, then add the third number; Or add the last two numbers first, and then add the first number, and their sum is unchanged, that is, (a+b)+c=a+(b+c).

3. Multiplicative commutative law

When two numbers are multiplied, the position of the exchange factor remains unchanged, that is, a× b = b× a.

4. Multiplicative associative law

Multiply three numbers, first multiply the first two numbers and then multiply the third number; Or multiply the last two numbers first, and then multiply them with the first number, and their products are unchanged, that is, (a×b)×c=a×(b×c).

5. Law of Multiplication and Distribution

When the sum of two numbers is multiplied by a number, you can multiply the two addends by this number, and then add the two products, that is, (a+b) × c = a× c+b× c.

6. The essence of subtraction

If you subtract several numbers from a number continuously, you can subtract the sum of all subtractions from this number, and the difference remains unchanged, that is, a-b-c=a-(b+c).