## The Lesson

Algebra is using letters (or other symbols) to represent an unknown number. An equation that uses algebra is called an algebraic equation (note that*algebraic*is the adjective for algebra).

## What Is an Algebraic Equation that Contains Addition?

An algebraic equation that contains addition is an equation with at least one letter being used to represent a number and with at least one addition.In the equation above, the x represents a number. In words, the equation means "x plus 4 equals 8". To solve the equation, we have to find the number that, when you add 4 to it, equals 8.

## How to Solve This Equation

**Question:**What is the value of x in the equation below?

So you just have x on the left-hand side of the equals sign, and the answer on the right-hand side:

The key to re-arranging an algebraic equation is:

Whatever you do to one side of an equation, you must do to the other side!

## Step-by-Step Approach:

# 1

Look at what has been done to the x.

# 2

Find the opposite thing to get x on its own.
The opposite to addition is subtraction, as shown in the table of opposites below:

The opposite of +4 is -4:

The opposite of +4 is -4:

# 3

Do this to both sides of the equals sign.

## The Golden Rule of Algebra

The golden rule of algebra is:**Whatever you do to one side of an equation, you must do to the other side!**Think of a pair of scales. The equals signs means that both sides of the scales balance:

If you do anything to just one side, the scales no longer balance and the equality no longer holds:

If you do the same thing to both sides, the scales return to balance, and the equality holds once again:

## Swap the Sides, Swap the Signs

Compare two of the steps in the step-by-step solution given on this page:You can think of this of as 'switching sides, switching signs'. The 4 has moved from the left hand side to the right hand side of the equals sign; and has changed to having a + to a - in front of it. This can be done to any term that is an addition or a subtraction.

## Equations ("Tetris" Game)

Here is an interactive game to help you learn about equations.**Tip**: If the game is playing slowly, you can use the controls below to remove the background text and image to speed up the game.

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