Theory:

What is an equation?
A pair of expressions separated by an equal to sign is called as equation. This equal to sign indicates that the pair of expressions are equal.
Example:
\(5x = 20\) is an equation. Here, \(x\) is a variable, the expression \(5x\) forms the left hand side of the equation (LHS), and the expression \(20\) forms the right hand side of the equation (RHS).
Now, let us discuss about linear equation in one and two variables.
 
1.Linear equation in one variable:
Linear equation is an equation in which only one variable is involved and having the highest power as \(1\). It is also known as simple equation.
Example:
\(5\) times \(x\) equals \(20\).
 
Solution:
 
The algebraic expression is given by:
 
\(5x = 20\)
 
This equation has only one variable and having the highest power as \(1\). This equation is a linear equation in one variable.
2. Linear equation in two variables:
Linear equation in which two variables are involved and having the highest power as \(1\).
Example:
\(5x + 6y = 8\), \(3x = 12 z\)