How do I detect which multiple old versions of directx are installed at the same time?

dxdiag says I have directx 12 installed. But some video games I want to play use directx 8 and 9 and the cd rom comes with the directx installer for the old versions. But if it did get installed, how do I check if the old versions have been installed? Dxdiag only shows the latest version of 12.