A linear equation is a mathematical statement that has a left hand side, a right hand side, and an equal to sign in between the two sides. There is one or more mathematical expressions on both the left hand side and the right hand side. A mathematical expression is a combination of operators and mathematical terms in proper and logical sequence. The two expressions in a linear equation, the one on the right and the one on the left, are equated by the equal to (=) sign present in between the two mathematical expressions. Thus this mathematical statement indicates that the mathematical expression on the left hand side is equal to the mathematical expression on the right hand side. This statement of equality is called an equation in mathematics.
A linear equation is a type of a mathematical equation in which the variable (the unknown quantity represented by an English alphabet or any other letter except a number is called a variable) or variables present have the greatest exponent as 1. Thus the degree of a linear equation is 1 and therefore any equation having the degree of 1 is called a linear equation in mathematics. The degree of an equation in mathematics is the highest exponent on any variable that is present in the equation's left hand side and right hand side expressions. For example, the following equation can be called a linear equation because the highest exponent present on any variable in the equation is equal to one:
3x + y = 4.
A linear equation can have one variable or more than one variables.