X usually brings to mind algebra. Solve for x. For most people, it's the first independent variable one comes in contact with. Up until algebra and pre-algebra, x simply meant to multiply numbers together. It was pretty simple. Pretty convenient. And then the Cartesian plane is introduced, along with the concept of solving a function, f(x), and childhood ends.
I've been fortunate enough to always enjoy mathematics, and I've always excelled in the field. That's probably part of the reason I went into engineering. That's probably the reason I took a job as an engineering calculus grader for a few years, where I got to check student exams and quizzes. I liked the beauty of math, the simple logic that said if you did this, then you can get this answer. And once I started getting deeper into calculus, once I started understanding roots and intercepts, once linear algebra somewhat clicked, my world opened up even more.
The cool thing is that so often we solve for x without even knowing we're doing that. If we're planning a road trip and know the distance and the speed we'll drive, we can estimate the time it'll take. Likewise, if we know a trip is about 2 hours away and we're going about 70 mph, we can figure that the location is somewhere around 140 miles. We make so many estimations and guesses without even thinking about it, and that is a form of numerical analysis and x-solving.
I love math. I do. It's fun, especially when it makes sense. There are upper echelons of calculus and mathematics that I can't begin to fathom, but the stuff that I do get, that's enjoyable.