Easy Algebra Lesson #2, Solving for x in a Subtraction Problem

Easy Algebra Lesson #2

In algebra, one or more numbers is replaced by a variable which is usually a letter. The most commonly used letters are x and y. Almost any letter can be used, but o is not used as it is easy to get it confused with the number 0. Sometimes even Greek letters may be used as variables, but oftentimes they mean something specific. There are some Greek letters that will not be used as variables because they stand for a certain designation.

Here is a very easy algebra equation.

x - 3 = 9

The first thing that needs to happen in order to "solve for x" is that the variable needs to be isolated. This means that only the variable should be on one side of the equal sign while all numbers should be on the other side of the equal sign.

Since the equation is x - 3 = 9, we need to get rid of the three.

In order to get rid of the three to isolate the x, a three must be added from the side with the x. However, in algebra, whatever is done to one side of an equation must be done to the other. That means that the three must also be added to the nine.

Thus, we have two arithmetical problems to solve. This first is x - 3 + 3 and the second is 9 + 3.

The answers to these equations are x and 12. Now that we have the answers to each equation, we can replace the equations with the answers. This gives us. x = 12. This also gives us the answer.

In the equation x - 3=9, x=12.

Then we can check the answer by replacing x with the solution. If x - 3 = 9 and x = 12, then does 12 - 3 = 9? If the answer is yes, the solution is correct.

Does 12 - 3 = 9? Yes. 12 - 3 = 9.

If we were to get an answer such as x = 14, we'd have to check our answer and we'd get 14 - 3 = 9. Does 14 - 3 = 9? No. 14 - 3 = 11.

Since we know that the answer is incorrect, we'd have to go back to our original equation of x - 3 = 9 and start over if we cannot find the error within our arithmetic.