Betty has 20 books, and her sister has 1/4 times more books than Betty. What's the total number of books the two have? Let's be accurate as possible.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Betty's sister has 1 / 4 * 20 books = 5 more books. The total number of books Betty's sister has is 20 books + 5 books = 25 books. The total number of books the two have is 25 books + 20 books = 45 books.
The answer: 45.