Algebra is a very important branch of math.
Algebra is a lot like arithmetic which means it follows all the rules of arithmetic, and it still uses the four main operations that arithmetic is built on.
In arithmetic, the only thing that was unknown was the answer to the problem. For example, 39 + 2 = 41. In algebra, we use a variable to represent the number. A variable is a letter that represents any number. The most common variable is "x".