"Using letters to represent numbers" is the teaching content of "One-dimensional Equation", the first volume of the fifth grade mathematics textbook of "Compulsory Education Curriculum Standards" published by People's Education Publishing House. This is the beginning for students to learn the basic knowledge of algebra, and it is also the basis for learning equations, inequalities, functions and other knowledge.

It is abstract for primary school students to represent numbers by letters. The numbers in students' minds are concrete and definite, while the numbers represented by letters are abstract and changeable, which is a leap in understanding. It is a long process for students to express numbers with numbers and letters, which requires a lot of activities and rich experience.

Alphanumeric:

The letters representing numbers contribute to the essential characteristics of concepts and make the relationship between numbers more concise and universal. Simplify the thinking process and easily form a conceptual system. Letters can represent any number, but only one number can be represented in a question.

It can also represent a formula with a specific meaning, a certain number that meets the conditions, or even a number with a certain law. In short, letters can concisely express quantitative relations. For example: a can represent a set; F(x) represents the function of x and so on. Representing numbers by letters is a great development in the history of mathematics.

When letters are used to represent numbers, numbers are multiplied by letters, letters are multiplied by letters, and the multiplication sign in the middle can be omitted. Or ""(dot).