done

I do admit it is pretty easy to cheese(and I feel dumb for not thinking of the dummy variable solution). I might try this again when/if I have the skill to prevent simple solutions like that(e.g checking if the variable influences the result) so the solutions have to be at least somewhat decent.

And I would fix the second issue, but the Kata's retired now, so no use.

approved by someone

Testing in most languages goes like userAnswer == expectedAnswwer
So your answer must match the author's expected answer which does not have a comma before and. (Note : in American English it is considered optional)

If you wish for a comma be to added, kindly open a suggestion stating that it should potentially be added.

But it will most likely not be added in -since it's not a great problem- and ~40k people who solved it would have their solutions invalidated.

but nonetheless this is not a Kata issue (this is programming site, not a grammer site)

What do you mean exactly? Where is it marked invalid?

It's been a while since I did this one, but I'm pretty sure I wanted the subtraction done first, not the multiplication.