Baseball cards
We know two things:
Gaetano had 52 cards on 3 years
Gaetano had 108 cards on 7 years
Then, from the fourth year to the seventh year he added
108 - 52 = 56 cards
In four years he added 56 cards. Then each year he added
56/4 = 14 cards
Since
14 * 3 = 42
On the first three years he added 42 cards to his collection.
Then he started with
52 - 42 = 10 cards
Answer: Gaetano started his collection with 10 cards and he adds 14 new cards to it each year