I have data arranged like this:

-----------Combo1---------Combo2
X-----------18-----------------15
Y-----------0------------------3
Value------5.44---------------7.63

So (18,0)--> 5.44 and (15,3)--> 7.63. Now different values of X and Y affect "Value". So it's two indepent variables affecting the depend variable, "Value".

I need to figure out what the exchange rate of X and Y is. In other words, i need the Ratio X=kY where k is a constant of some sort.

My first strategy was to generate 2 random pairs of values for (X,Y) that both give the same "Value". Then, i could deduce the ratio. E.g. If (10,0) and (15,10) give the same Value, then the ratio is 5X=10Y or X =2Y. But this has proven difficult because the values are difficult to generate!

How could i determine the ratio strictly from the 2 columns above (keeping the Value(s) different)?! Is this possible?!