My thinking is that if I add a spirit (tequila, rum, maybe both
...etc.) to a finished beer at packaging, the new ABV would be a balancing equation of volumes and ABV's:
(Vol1*ABV1 + Vol2*ABV2 +Vol3*ABV3 etc.) / (Vol1+Vol2+Vol3 etc.)
Or is there more to it than that? And if there is more to it than that is it really worth the extra effort in figuring it out?