Answer:
 14
Explanation:
You want the number of my cats when that number is "one-half of my cats plus seven".
Setup
Let the number of cats be represented by c. Then the description of the number of cats is ...
 c = c/2 +7
Solution
Multiplying by 2 gives ...
 2c = c +14
 c = 14 . . . . . . . subtract c
The nemesis has 14 cats.