I cut each of the three tablets in half, and created two piles (i.e. as I broke each tablet, I placed one half in the left pile and the other half in the right pile).
Each pile now had one half of Anvilite, and two halves of Bigoxy.
All I had to do was to split another Anvilite tablet, and place half in each pile, so each pile then had two halves of each tablet (i.e. a whole tablet), which is exactly how many I had to take.
I had one pile last night, and the other pile is for tonight.