__equations__ and __expressions__

__equations__

__expressions__**__________________________________________**

## Sometimes an __equation__ has a unknown number

__equation__**13 - 7 = ? 3 x 4 = ? 10/2 = ?**

## instead of using a question mark

for the unknown amount,

we use a* *__variable__ -- a symbol like **N** **Y **or ** x**

__variable__**5 + 25 = N 5 + 25 = Y 5 + 25 = x**

## the symbol that represents an unknown amount is called a* *__Variable__.

__Variable__## solve the equation to find x

5 + 25 = x

30 = x

5 + 25 = x

30 = x

## the __variable__ can be on either side of the equation & mixed in with the __constant__ numbers.

__variable__

__constant__**2 + x = 5 n x 10 = 90 4 = 8 - y**

__constants__ are the known numbers.

**variables** are the unknown numbers.

the **=** sign separates the equation

into 2 equal sides.

__constants__

**variables**
## An
expression |
2 + XN x 10 8 - Y |