formula states the realationship among unknown quantites? what would be an example?

Answer 1

Every formula states the relationship between unknown quantities. That's what a formula is!

One formula I know is:

PV = nRT

This is called the ideal gas law. It means that the Pressure (P), the Volume (V), the Number of molecules of the gas in moles (n), and the Temperature (T) are all related by a constant (R).

That's 4 unknowns and a constant.

If you know any 3 of the unknowns (say pressure, volume, and number of molecules), you can calculate the fourth (temperature).

Answer 2

R = V/I Ohm's Law

Resistance = Voltage/Current