I was given a TI-84 Plus Silver Edition calculator from a friend. The calculator works great, but I am running into a problem using variables. Whenever I try to solve or graph equations using variables in them such as "x", the letters seem to have specific numbers assigned to them. Though the letters don't show the numbers assigned to them, the results I get from plugging in equations and graphs with variables is incorrect, making it clear to me that there is some data that has been stored that I need to delete. However, I can't seem to find any information in the manual on how to delete this information. I would like to delete all stored values, as I don't want it causing me any problems down the road with having incorrect values in equations during any courses.

I'm thinking the best bet might be a full reset of the calculator to all defaults (if possible), but I don't know what I might lose in that process as well. If anyone can tell me how to solve this issue and ensure it won't cause me any grief down the road, I'd really appreciate it.