Yes the "-" is a "don't care"
I was thinking the same thing as gorgon about taking advantage of the inbalance between the number of 1's and 0's. However I have to take that back. Here's why.
The final truth formula will a series of terms. Each term OR'd together. Within each term will be one or more expressions AND'ed together.
For instance we might have Q = (A AND B) OR ((NOT A) AND C) OR (NOT C)
That is 3 terms.
If we were concentrating on the 0's we might have ended up with that as a FALSE formula we would still have to NOT it. So the truth of Q would be:
Q = NOT((A AND B) OR ((NOT A) AND C) OR (NOT C))
But that "NOT" at the beginning can't stay there. When we force this into the proper form of TERM OR TERM OR ... that "NOT" might make things real messy. It might or it might not, but the point is we don't know, so just starting out with isolating the 1's rather than the 0's is the way to go.
About the request to the OP to post his answer... I asked for that, too, but now I have to take that back as well. I think the image that the OP posted IS HIS ANSWER. The next step after doing a Karnaugh Map would be to write the truth expression. (Q=...) Each grouping in the K-map will be an term in that expression, but in this step I think the assignment is to just circle the best groupings.
Steve! Nice what you did with the one red block wrapping around all 4 corners. And you got it to 5 groups.
I think I see one more way to simplify it. If your purple group is shifted down by one row, it will snag the 1 in the top row. And then the blue group can be eliminated.
Down to 4 groupings.
-t