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Solving Addition and Subtraction Equations

In it's essence, Algebra is solving equations for unknown values.  There are times that you'll be able to do this in your head (for the very simple equations), but it's best to follow the rules that will work for every problem!  Let's have a look:

X + 1 = 3

Of course, it's easy to do this in your head.  X will equal 2 because 2+1 is equal to three. We'll use this as an example to show how to do the harder ones.

Step 1:  Isolate the variable.  That's a clever way of saying "get X (or other unknown value) by itself." This means that you want your equation to look like X = Value.  To do that, we perform the same operation on both sides of the equal sign to make X all by itself.

X + 1 = 3
To get X = Value, we need to get rid of the 1.  Since the problem is X + 1, we can subtract the 1 to make X by itself:

Remeber:  Whatever operation you do to one side of the equation (one side of the equals sign), you MUST do it to the other side!   Since we subtract 1 from the left side of the equals sign, we must also subtract 1 from the right side of the equal sign!

This works the same way as addition.  
Here is an example:  X - 2 = 9

In order to get the unknown X value by itself, we add 2 to the left side - so we must also add it to the right side. And that's all there is to that!

Ready to work with some Multiplication and Division Equations?

Find another math lesson at the Math Lesson and Tutorial Center!

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