OK, I'be been pounding my head against the wall all morning to trying to figure this out.

This is a real world problem.

1. I have an equation such that X divided by Y = Z.

2. Then, X and Y change at the same time.

3. The difference in Z between Original and Revised in this example is 18,800.

4. I'd like to explain or "break down" the 18,800 in terms of X and Y. "I.e, Of the 18,800, ____ was due to change in X and ____ was due to change in Y."

5. I thought I could understand the impact from each variable by changing one at a time and then add their impact but, it's not equal to changing both at once.

6. How can I quantify the "contribution" that X and Y made discreetly to 18,800??????

See attached image for graphical representation of the problem in table form.