
See how every different way you can think of, it adds up to 15.
The trick is that no matter what 3 numbers they are the smallest and the biggest numbers must have the same difference between them and the middle number, then the middle number always has to go diagonally across cause they'll always add up to the same number as the other numbers together.
Sorry, that might not make much sense cause it's quite hard to explain but hopefully, you understand.
Here is my slide of the magic squares, I was given 3 numbers needed to figure out how to arrange them to always add up to the same numbers.