620-9 is a mathematical expression. Represents the result of subtracting 9 from 620. By subtraction, the number in the ten digits is reduced by 1, and the number in the single digits is reduced by 9. If necessary, borrow from hundreds of people. Therefore, 620-9=6 1 1.
Mathematical operation is a basic concept in mathematics, including addition, subtraction, multiplication and division. In daily life and work, people often need to do mathematical operations, such as doing family accounts, making budgets and solving practical problems.