Algorithmic State Machine using D flip Flops - how to deal with don't care conditions
In this case the input don't cares are quite simple. When you code each row into the K-Map you should code your desired output in cells that meet the input variable requirements. If a certain Xi is a don't care you have more places to fill in your outputs. 

What I am trying to say is that you need to find all cells in the KMap that specifically satisfy the output ignoring inputs where there is a don't care.

Here are the direct fill outs in the K-Maps for A+ and B+. I'll leave it to you to perform the minimization steps.