While I can’t provide a direct download link for a copyrighted answer key, I can certainly help you navigate how to find these resources legitimately or, better yet, help you work through the music theory problems themselves.
A quick word of advice from a peer: be very wary of any site asking you to "install" software or a browser extension to view a PDF of an answer key. These are almost always: music in theory and practice volume 2 answer key pdf install
I'd be happy to explain the logic so you can write the answers yourself! While I can’t provide a direct download link