Abandoning nine and ensuring ten is the method of abandoning nine in mathematics. Abandon the nine method and use the characteristics of decimal numbers to test the results of addition, subtraction, multiplication and division of several numbers. Nine-elimination method, also known as nine-elimination method and nine-elimination method, is a method to check addition, subtraction, multiplication and division operations. Its application can be traced back to Sassanian dynasty, when Islamic cultural trade flourished, and the business demand produced nine methods to check the operation in the transaction.