Answer:
Algebra is a abstract way of thinking about things. We usually see this by defining things we don't know as some sort of symbol (Matter of fact. All of Mathmatics revolves around symbols). It doesn't necessarily have to be a number. I could label some big brown sturdy thing with green stuff on top as a tree which in a mathmatical sense the tree would be the variable and the actual thing would be the thing inside of the variable. But basically it's an abstract way of thinking
Explanation: