What is the unknown of a mathematical equation?

For example, in the equation $X+5=8$

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.

$X+5=8$

$X+5-5=8-5$

$X=3$

If this article interested you, you may also be interested in the following articles:

• First-degree equations with one unknown
• Equivalent Equations
• Transposition of terms
• Solving equations by adding or subtracting the same number from both members
• Solving equations by multiplying or dividing both members by the same number
• Solving equations by simplifying equal elements
• Solving equations by using the distributive property

In the Tutorela Math Blog you will find a wide variety of articles about mathematics.

$14x+3=17$

Solution

We subtract $3$ from both sides of the equation, that is:

$14x+3-3=17-3$

$14x=14$

We divide by $14$ both sides of the equation:

$14x/14=14/14$

Answer

$x=1$

Find the value of x in the following equation:

$2x+7-5x-12=-8x+3$

Solution

We pass the numerical values to the right and the coefficients that are multiplying to $X$ to the left.

$2x-5x+8x=+3-7+12$

Reduce and add as much as possible.

$5x=8$

We divide by $5$ both sides of the equation:

$x=\frac{8}{5}$

Answer

$x=\frac{8}{5}$

Find the value of $X$ in the following equation:

$5x=0$

Solution

We ask which number multiplied by $5$ is equal to $0$ and the answer is $0$

$5\cdot0=0$

Answer

$x=0$

Find the value of $X$ in the following equation:

$5x=1$

Solution

We divide by $5$ both sides of the equation to find out how much is the value of $X$

$\frac{5x}{5}=\frac{1}{5}$

$x=\frac{1}{5}$

Answer

$x=\frac{1}{5}$

Find the values of the variables so that the following equation is well defined:

$\frac{25a+4b}{7y+4\cdot3+2}=9b$

Solution:

We must calculate for which values of $Y$ the denominator of the expression on the left-hand side of the equation is equal to zero, i.e.:

$7y+4\cdot3+2= 0$

$7y+12+2=0$

$7y+14=0$

We subtract $14$ on both sides of the equation and we obtain:

$7y=-14$

Divide by $-7$ on both sides of the equation:

$y=-2$

If y equals minus $2$, then the denominator equals $0$ and the equation is not well defined:

$y\operatorname{\ne}-2$

Answer

$y\operatorname{\ne}-2$

The variable and the fixed values or numbers.

It is the unknown value to be found.

Variable

Clearing the unknown with the mathematical operations that are addition, subtraction, multiplication and division.

Dividing by the factor that is multiplying the unknown.