When using two studio lights and metering for a portrait.

If I have a Main Light to camera left and Fill Light on camera axis and using f11 as shooting aperture.

If I meter the Main to f8 and the fill to f5.6 this should come close to f11 (but not exact)

In my calculation f8 + f8 = f11, but then there would be no contrast.

I would be off by f8 - f5.6 if I used f8 + f5.6.

Realize the light scale between f.56 to f8 is not linear.

So just for the sake of brain twister what is the value of f8 - f5.6 ?

and what is the value of x in f8 +fx = f11