Based on teeth I would say 6-7 years old, but then again it could be they weren't taken care of before. I have a nine year old and her teeth have no tartar and one would think by her teeth she is two .
Misty- Samoyed Mix
Tannor- Golden Retriever CGC
Robyn- German Shepherd CGC, TC
Midnite-German Shepherd CGC, TC
Brennan- Golden Retriever CGC