**The solution of an equation is, in fact, a numerical value that, if we place it in place of the unknown (or the variable), we will achieve equality between the two members of the equation,** that is, we will obtain a "true statement". In first degree equations with one unknown, there can only be one solution.

**Example:**

$X - 1 = 5$

This is an equation with one unknown or variable indicated by the letter $X$. The equation is composed of two members separated by the use of the equal sign $=$. The left member is everything to the left of the sign $=$, and the right member is everything to the right of the sign.

Our goal is to isolate the variable (or clear the variable) $X$ so that only it remains in one of the members of the equation. In this way we will discover its value. In this article we will learn how to use the four mathematical operations(addition, subtraction, multiplication and division) to isolate the variable $X$.