The notion of **unknown** , derived from the Latin word *incognĭtus*, refers to what results **unknown** . The term has different uses according to **context** .

For example: *"The current level of the basketball player is unknown because he hasn't played for seven months"*, *"The mystery ended: the president announced that he will run again as a candidate and will aspire to re-election"*, *“The singer did not clear the mystery and still does not confirm whether or not he will return with his old band ”*.

In the field of **mathematics** , it is called an unknown **unknown quantity** that must be specified in a problem or in an equation to achieve its resolution. It can be said, therefore, that a mystery is one of the elements that constitute a mathematical expression.

In a **equation** , the unknown is an unknown value that, when discovered, allows to verify equality. In a problem, there may be several unknowns, each expressed by a symbol that cannot be repeated.

The problems that are solved with the **rule of three** , to cite a case, they are based on the presence of an unknown and three **values** known. Among these elements there is a linearity relationship given by proportionality.

If we know that, in a **restaurant** fast food is sold **a hamburger** to **50 pesos** , and we intend to buy **three hamburgers** , we can resort to the rule of three to know the total price that we will have to pay, discovering the value of the unknown:

If a hamburger costs 50 pesos, three hamburgers cost x pesos.

*1 hamburger = 50 pesos3 burgers = x pesos(3 × 50) / 1 = x150 = x*

This means that the unknown has a value of **150** : three hamburgers cost **150 pesos** .

This is also known by the name of **simple three rule** , to distinguish it from the **composed** , in which there is a greater number of **magnitudes** which are used to find out the value of the unknown. In addition, in the example of hamburgers we are facing a simple rule of three case **direct** , since all magnitudes increase or decrease in the same direction, with a *direct proportionality*.

We can explain this by thinking of each one of them: we have the **price** from **a** hamburger which is **fifty** pesos, and we want to find out the one of **three** burgers. Well, if we increase any of these three values, we will be forced to increase the other two **in the same proportion** : if we knew the price of **four** hamburgers, that is to say if we multiplied by four the previous data, then the two remaining quantities would be **Two Hundred** weights and **twelve** burgers.

The concept of incognito has been part of mathematics for centuries, always with the aim of modeling algebraic problems of polynomials, that is, of expressions formed by a finite amount of variables and products between constants and variables. As alien as the mathematical theory may seem to us in everyday life, it could not be more present: every day we make decisions related to amounts, with amounts of money, with the order of things in a system, etc., and for all that and much more we use this **science** automatically

This brings us to the seemingly negative nuance that the term receives *unknown* in everyday speech: although it can also serve to denote mystery in an attractive sense, it is usually used when this lack of knowledge causes us an inconvenience. In mathematics, it is thanks to this doubt that problems exist, and it is they who move forward knowledge, the very reasons for research and constant learning. If there were no things to solve, then everything would lose **sense** , since life would become static.