Make sure you understand what "no more than" means.
If you have no more than 10 books, that means you have 10 books or fewer.
The number of books is less than or equal to 10.
No more than 53 means "<= 53", less than or equal to 53.
Let the number be x.
The sum of a number and 7 is x + 7.
x + 7 <= 53
