I write an “x” by drawing two straight lines that cross in the middle, the first from upper left to lower right, and the second from upper right to lower left. But I’ve been watching the Youtube channel “Stand-up Maths” by Australian mathematician Matt Parker, and I notice that he writes his "x"s in a different way. He draws a curved line from upper left to lower left, like a backwards “c”, then a second curved line from upper right to lower right, like a forward “c”, so the two curves touch in the middle. I’ve never seen anyone else write an “x” like this. Is this a standard Australian style, or a personal idiosyncracy, or perhaps a more widespread style that I’ve just never noticed before?
This is how I was taught to write an “x” when I was a kid (early 80s, Europe) but now I use an alternative version of yours : a straight line from upper left to lower right, then one from lower left to upper right.
It’s a standard developed in math to distinguish x, the variable from × , the multiplication symbol.
Yeah, I was taught to do an X the way Matt Parker does specifically for Maths algebraic notation. Though an x as multiplication is also discouraged anyway.
btw, I draw an X from top right to bottom left as my first stroke.
Is this a new convention? I graduated with a BS in mathematics in 1978 and never noticed any of my professors write it that way. Also as GuanoLad says it’s unusual to use an x to denote multiplication in higher math, in most contexts, so I don’t see the need for it.
I was taught (in maths and physics) at secondary school to write x in that way (England, late 1970s).
Possibly of note, this teaching was part of the introduction to algebra and other stuff we had not dealt with at primary school, so it probably makes sense in that context that there is a clear distinction between the letter X and the multiplication symbol which we had learned at primary school.
My experience in South Africa in the mid 90s was the same for the same reason. And we were taught the curved x as we were taught to drop the X for multiplication in equations.
I was never taught this alternate x, but it makes sense to me. I wrote a few letters/numbers differently in certain math and engineering classes to keep things clear.
(ETA: I would use a “cursive” x, with swoopy lines, but drawn top left to bottom right, top right to bottom left.)
I started drawing a line through my 7s and added that to my Z as well (both upper and lower case), to distinguish it from 2 (which I don’t draw consistently with a clear loop, it seems). I don’t put a serif on my 1s, they’re just vertical lines.
My capital G has the bar hanging down, almost like a q. Helps me distinguish it from a 6. Since the loop isn’t closed, it doesn’t look like my 9.
I also got frustrated in fluid dynamics with equations that had both a capital V and lower case v (volume and velocity, I think?). So I’d put a horizontal bar across the capital V so it looked a little like an upside down A (the bar would stick out though). The teaching assistant commented on it, that he appreciated that this made my work clear.
I agree - the curved X is for algebra. The way I learned to do an X was cursive, so you draw a hump left to right, then go back and put a downward right-to-left cross (since your had has ended up on the right of the hump.) This is the opposite of crossing your T (not capital) in cursive, which I do from left to right.
of course, if your x follows some letters like O where the pen ends up at the top, to make an X instead of a hump you just go straight across a little bit then down on the diagonal. (same with VX, BX, WX)
When printing an X, I do left-high downward to low-right, then since my pen is on the right of that, right to left downward to finish the letter. It seems to flow better to loop the pen up and around than down and around to start the second stroke at the bottom left.
In Pakistan in the 1970s/80s that’s what we were taught.
I tutor math and some of the students have commented on this.
I also use this form of X when writing cursive.
By the way, my students have found that writing exam answers in cursive is problematic. The graders cannot reliably read cursive. So the ones who learned cursive (typically who attended Catholic elementary school) have to learn to print the answers.
I do write the x different from the multiplication symbol—with serifs, similar to how it looks in print when properly typeset—but I do not draw it the way the OP describes. Instead, I write the part that goes from upper left to lower right and then the other part that crosses it.
Same as the other posters: curved x for algebra, cross bar x for letters.
Unicode has a code for “Mathematical Italic Small X”, so it’s pretty clearly established.
I graduated with a BS in math in 2002 and also never learned that. I don’t even recall seeing it, or at least not thinking anything of it if I did. FWIW, I watch most of Matt Parker’s videos and never noticed him doing it either. But not knowing it’s a thing, I would’ve assumed it was just how he wrote it.
At least for me, if I’m doing something where that could be confusing, I’ve used a dot (or parentheses) for multiplication.
I do, however, put a line through the letter Z. Previous to doing that, there were too many times when I had to go back through quite a bit of algebra chasing down a problem only to find that I turned a Z into a 2 or vice versa somewhere along the line. At least that problem tends to reveal itself sooner than accidentally flipping a sign, which you might not realize until the final answer doesn’t make sense.
That’s why the European 7 makes so much sense; it’s not possible to confuse it with a 1.
Unless you have bad handwriting and you confuse it with a Z (with a line through it).
That’s crazy talk 
I happen to write an “x” as two crossing lines, but the lines forming a handwritten x are not straight, so the symbol is not really mistakeable for a cross product.
The only convention, not new, that I am aware of concerns typeset mathematics, in which variable names are in italics, as distinct from Roman.
That is what I think, namely that the different forms are a function of what model students are being taught to use for their handwriting: round hand, Spencerian, Palmer, etc. There is a lot of regional variation.
One does use different “fonts” in mathematics: Roman, Italic, Blackletter, etc., but it does not mean one should or is supposed to play games with minuscule differences when it comes to handwriting. a versus \alpha is bad enough, not to mention \pi versus \varpi or \theta versus \vartheta…
Australian here - its a mathematics convention as others have said, not the way we’d usually write it in xylophone or x-ray, at least those of us taught proper.
The Latin script is not like Chinese characters, where the sequence and direction of the strokes is exactly prescribed. One would therefore expect that many different variations exist. My personal way to write x is the one described by @Moonrise: upper left to lower right, then lower left to upper right.
It might be out of favor to use × for standard scalar multiplication, but it’s still used in many other contexts in math, such as cross-multiplication of vectors (where there are other forms of multiplication represented by a centered dot, and by direct concatenation, that must be distinguished from it).
What always strikes me as odd is that modern calculators all still have a button labeled ÷ , but if you press it what appears on the screen is a / .