Just to start off, we need to know what variables are. Well, here's the best way to put it:
Variable: A variable is a quantity that can change or vary and is often represented with a letter.
What that means is that in algebra, we can represent numbers as letters!
How To Write Expressions With Variables...
Well, when you are expressing any situation in algebra, you will need to use variables. Let's take a look at an example of such a situation. So, let's say that we have 23+46=69 and we have to replace 69 with a variable. Remember that variables are just letters, so that means that we can just simply take any one of the twenty-six letters, and replace it with 69. Usually, the variable will be x, but not always! I will use r, for this case. That means that our now algebraic expression is: