- Books Name
- CBSE Class 7 Mathematics Book

- Publication
- Param Publication

- Course
- CBSE Class 7

- Subject
- Mathmatics

**Variable**

It means something that can vary or change. It takes different numerical values. Usually variables are denoted by letters of the alphabets. For example, x, y, z, a, b, c etc.

**EXPRESSION**

Expressions are obtained by placing mathematical operators like addition, subtraction, multiplication and division on the variables.

** For example, 2 x + 3**

This expression is formed by multiplying x by 2 and then adding 3 to the product.

**EQUATION**

An equation has always an equality sign. An equation can be formed by using equality sign between two expressions with the condition that these two expressions should have equal value. Atleast one of the two expressions should have equal value. The equality sign means the value of the expression to the left of the sign is equal to the value of the expression to the right of the sign.

An equation remains the same, when the expressions on the left and on the right are interchanged.

** For example, ** 2x + 3 = 5x –5 is same as 5x–5 = 2x +3