The essence of continuous subtraction: if a number subtracts two numbers continuously, the sum of the two numbers can be subtracted. ?

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

For example:128-57-43 =128-(57+43)?

Memory: decrease, increase, unchanged.

The nature of continuous division: a number divided by two numbers can be divided by the product of these two numbers?

Formula: a÷b÷c=a÷(b×c)

For example: 2000 ÷125 ÷ 8 = 2000 ÷ (125× 8)?

Memory: multiplication has not changed except for change.

Multiply two numbers, one of which can be split, and then simply calculate.