I am a middle school student who would really appreciate it if somebody could explain how to solve this problem using simple terms. I saw this problem on this site and one other, but I am still unsure of how to get $384$ like the solution said here: Mini Sudoku -Critique of Solution-
In this circumstance -with $16$ available slots- there are $384$ possible combinations with over-counting.
And here is the problem:
Let's play mini-Sudoku!
We wish to place an $X$ in four cells, such that there is exactly one $X$ in each row, column, and $2\times2$ outlined box. For example:
In how many ways can we do this?
Terminology: A cell is one of small $1\times1$ spaces. A box is one of four outlined $2\times2$ group of cells. Please use this terminology so there is no ambiguity between you and your audience.