Magic square hint

The problem posed was this.

In this grid the three numbers in each row, column and main diagonal must add up to the same total. Find the missing numbers.

22	14
	0	25

This is tricky! So here's a big hint for getting into it.

The number in the shaded square below must be equal to 22 + 14 – 25. But can you work out why?

22	14
	0	25