I think that what is going to happen in the solution is that the "-D11" is going to go over onto the left hand side. You'll bring the "D10" across to the right. After doing this, you'll go through some algebra on the right hand side which will enable you to cancel out the Logs on the right which have the "D11"s in them.

Good luck doing it though, it's a bitch of a question :) If you post it on the maths forum at vbforums.com you'll get the answer for sure.
Cheers,
Michael Bray