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Solve for x

An equation is a balance

x + 3 = 7
x + 37x + 3 = 7subtract 3 from both sidesx = 4

Both sides of an equation must stay equal. Think of the equals sign as the center of a scale.

Detailed notes

Worked Example

Solve x + 3 = 7 by doing the same operation to both sides.

Step 1: Start with the equation

The equals sign means both sides have the same value.

x + 3 = 7

Step 2: Undo the extra number

The variable has 3 added to it, so subtract 3 from the left side.

x + 3 - 3

Step 3: Keep the equation balanced

Whatever you do to one side, do to the other side too.

x + 3 - 3 = 7 - 3

Step 4: Simplify

The +3 and -3 cancel. The remaining value of x is the solution.

x = 4