Additive associative law; a+b+c=a+(b+c)

Multiplicative commutative law: a*b=b*a

Law of multiplicative association: a*b*c=a*(b*c)

The law of multiplication and distribution ab+ac=a(b+c)

A number can be continuously subtracted from two numbers, and the sum of these two numbers can also be subtracted:

a-b-c=a-(b+c)

When a number is divisible by two numbers in succession, it can be divisible by the product of these two numbers: a/b/c=a/(b*c) These are simple calculation laws in primary schools.