Impossible to give an absolute number but you could make an expression.
If you take a rectangle, and count the height and width twice, you'll add up with the perimeter.
So you could say:
[tex]P = 2W + 2H[/tex]
We could rewrite that to say:
[tex]25 = 2W +2H [/tex]
and then
[tex]2W = 25 - 2H[/tex]
So
W = 12.5 - H
