But before explaining whatunknowns are, it is important that we review the concept of what a mathematical equation is:

An equation is an algebraic expression that includes numbers (fixed values), and also letters with unknown value (unknowns). Our goal is to arrive at a solution to the equation, that is, to find the missing value (the unknown), so that both sides of the equation are equal.

What is an unknown?

In general, we express the unknowns with the letters$X$,$Y$ or Greek letters such as alpha and beta. Most of the time we will be asked to find the unknown value to be determined by solving an equation.

In this exercise $X$ is the unknown to be found, and for this we will have to clear it. In this simple case all we have to do is subtract $5$ from both sides, and we will arrive at the answer.

$X+5=8$

$X+5-5=8-5$

$X=3$

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