In algebra (UGH!) X usually represents an unknown number that you must solve an equation to find.
I am not a fan of algebra. I am even less a fan of geometry (too many formulas to remember). I was never good at memorizing things and even less so when it came to anything having to do with numbers. I also have a disorder known as Dyscalculia, which is difficulty in learning or comprehending arithmetic such as difficulty in understanding numbers, learning how to manipulate numbers, and learning facts in mathematics which turned up in junior high school (what would now be called Middle School) when my parents were attempting to figure out what my major malfunction was.*
Long story short, I was given a number of tests. The results were that my vocabulary and reading comprehension were college-level and my math level was approximately third grade. The problem was not overall intelligence (my IQ is above-average), it was determined that I have fundamental issues with both numbers and logic. (The logic part is something I think that most all of the men I’ve ever known would agree is a completely missing element in my thought process *grin).
Anyhow, math has gotten marginally easier for me as I have aged. I find myself remembering some “tricks” for doing calculations that have helped a lot. I am beyond thankful that I did not go to school in the era of “Common Core” because I look at “Common Core” math and totally shut down.
*The bottom line was that this was the age where I actually started not accepting everything my parents said as something that should go unquestioned and they weren’t dealing with that well. The math issue was especially problematic as my stepfather, who I did not get along with, was a math teacher at the local vo-tech college. So, admittedly, there may have been some sort of issue with my not-so-friendly feelings toward my stepfather that impacted my “give a damn” about math.