Answer:
5.5 years old.
Explanation:
Let D represent present age of Robert's dog and C represent present age of Karen's cat.
We have been given that Robert's dog is 4 years older than Karen's cat. We can represent this information in an equation as:

We are also told that in 3 years, the sum of the ages of Robert's dog and Karen's cat will be 13. After 3 years age of dog and cat would be
and
respectively.
We can represent this information in an equation as:

From equation (1), we will get:

Upon substituting this value in equation (2), we will get:

Combine like terms:





Therefore, Robert's dog is 5.5 years old right now.