2. Calculate the contents in brackets: 55-45= 10.

3. Calculate the multiplication: 10x32=320.

Simple calculation is a special kind of calculation, which makes use of the algorithm and the basic properties of numbers, thus making the calculation simple and making it easy to calculate numbers from very complicated formulas.

1, multiplicative distribution law

The most commonly used method in simple calculation is multiplication and distribution law. Multiplication and division means ax(b+c)=axb+axc, where A, B and C are arbitrary real numbers.

2. Multiplicative associative law

The multiplicative associative law is also a simple operation method, which is expressed by letters as (a×b)×c=a×(b×c).

3. Multiplicative commutative law

Multiplicative commutative law is used to exchange the positions of various numbers: a× b = b× a.

4. additive commutative law

Additive commutative law is used to exchange various numbers: a+b = b+a.

5. Additive associative law

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