Question 620606
Hint:

Draw a venn diagram like the one shown below


<img src="http://i150.photobucket.com/albums/s91/jim_thompson5910/Algebra%20dot%20com/06-13-2012.png">


Note: the region ABD for instance represents the region where the sets A, B and D overlap. Relabel sets A, B, C, and D with the dog breeds (and the "unknown") if you need to.