Math set of users to a standstill

One of the Twitter users asked a task which he called funny "mathematical meme." His answer to a fairly simple example of a set of users to a standstill, because the decision, in their view, was quite different.

A maths meme that is actually funny rather than stupid:
Solve carefully!
230 - 220 x 0.5 =

You probably will not believe it but the answer is 5!#maths

- KJ Cheetham ❄️ #FBPE 🔶 (@kj_cheetham) July 13, 2019

Mathematical meme that is really funny, but not stupid:
Decide carefully!
230 — 220 × 0,5 =
You probably will not believe it, but the answer is 5!

In the comments, many users have begun to argue that the correct answer - 120, as a multiplication is performed first, and then later subtraction. Others added that the answer 5 is only possible if there are brackets: (230 — 220) × 0,5. However, they are not here, which means that 120 - really the right answer.

In fact, this is a tricky task, which the author warned by the words "Decide carefully!». Few people realize that the answer is not "5" and "5!", Ie the factorial of a number, which is indicated by an exclamation mark.

Factorial - a function that is defined as the product of all integers from 1 to n inclusive. In this case, 5! = 5 × 4 × 3 × 2 × 1 = 120. In other words, users answer in the comments was true, but the author hid his function.

And were you able to understand at once what was the catch? Share in the comments.