Answer:
C. 25 years
Explanation:
From my understanding you were asking to;
Double Allan's age, which is three, so double of his age would be six
Subtract Allan's age, three, from George's age, seven, and you would get four
Add George's age, seven, to Juan's age, eight, and get fifteen
Then you asked to add all the results together which would be;
6 + 4 + 15
That would equal 25 and since we were measuring years it would be 25 years, not just 25.