I'm trying to create a magic square

Question

I'm having trouble trying to make a $3\times3$ magic square with magic number $12$ and I can't figure it out.

Can you please help me?

Answer 1

You need to:

Subtract $1$ from every entry of a magic square with magic number $15$:

 8 1 6  -->  7 0 5
 3 5 7  -->  2 4 6
 4 9 2  -->  3 8 1

Answer 2

Alternatively to @JonMarkPerry 's answer, if you don't want to use zero in your answer and you do want to use decimals,

all you need to do is come up with some 9-number sequence whose average is 4. Enter the sequence, in order, into the bottom cell, the top right cell, the left cell, the top left cell, the middle cell, the bottom right cell, the right cell, the bottom left cell, and the top cell. This process will work for any nine-number sequence; the magic number will be three times the number in the middle of the square. In my magic square, the sequence is 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6.

 3.5| 6 |2.5
 ---|---|---
  3 | 4 | 5
 ---|---|---
 5.5| 2 |4.5 

There you go! Enjoy!