if the reaction is 1:1 (one unit to one unit)
Then the percentage is:

(min : max) * 100

example: 90 units A and 120 units B

(90 : 120) = 0.75
0.75 * 100 = 75%


example: 55 units A and 7 units B

(7: 55) = 0.127
0.127 * 100 = 12.7%

right.. i know! but to calculate the min and max of 2 numbers .. thats the point

because if you have 90/120 and what if you have 120/90 that wont work, so it must know the min, and you dont want to out that, thepc should calculate from what you have..

So i forgot the mnual , there is that function min(a,b) lool so much work

Wouldnt this do what you are after?
result = minv(x,y) / maxv(x,y); as a 0.0->1.0 result
or
result = minv(x,y) / maxv(x,y) * 100; as a 0->100 (%) result

yes it would.. but i didnt know there was a minv :S lool other wise i would avoid that math stuff lol.. well but it was fun to go trough it lol

come on, even of there where no min function,
you could use
if (a>b) max=a: min=b;
else max=b;min=a

you should be able to figure that out...