Double Math

What is the Value of x?

‘X’ is used in algebra as a variable. It is often used for unknown values. 

‘X’ is sometimes called ‘unknown’.

Variables can be letters, numbers, symbols, or a combination of those. It does not have to be “X”. It can be either “Y” or “W”.

For example:


x =5-1

x =4

Here x is unknown and the value for x is 4.

How Do You Solve for x?

Solve the equation for x by putting the variable on one side and putting all the remaining values on the other side. Calculate the result by simplifying the values.

Let’s solve the equation as

 x + 5= 9

Subtract 2 from both sides

⇒ x + 5- 5 = 9 – 5

⇒ x = 4

Now, check the answer, x = 4 by back substitution in the equation. We get 4 + 5= 9.

L.H.S = R.H.S

To find an unknown angle in a triangle

Using properties of triangles or the Pythagorean theorem, we can solve for x  the unknown side or angle in a triangle.


solve for x in a triangle 

△ ABC is right-angled at B with two of its legs measuring 3 units and 4 units. Find the hypotenuse x.





Solve for Equations

We solve two equations for x,

x-4y=4 eq(1).

4x-y=16 eq(2).

From eq(1)

Derive the value of x

x=4+4y eq(3).

Put it x=4+4y. in eq(2)

4(4+4y)-y =16.

16+16y-y =16.

15y = 16-16.


Put y=0 eq(3).




[x,y] =[4,0].

Solve for x in Fractions

we simply do the cross multiplication and simplify the equation to find x.

\frac x{20}=\frac3{10}.

Multiply both sides with 20.

\frac x{20}\times20=\frac3{10}\times20.