Answer: John has 17 dogs.
Explanation:
Lets start by giving each of the names a variable, so John will be J and Carlota will be C. Then let's write out the equations that are given to us.
The first sentence says "John has 6 more dogs than Carlota."
J = 6 + C
The second sentence says "Together they have 28 dogs."
J + C = 28
Now, we can substitute the first equation in the second one.
(6 + C) + C = 28
And solve!
6 + C + C = 28
2C + 6 = 28
2C = 22
C = 11
Knowing that Carlota has 11 dogs, we can substitue that back into the first equation to get:
J = 6 + 11 = 17