To find out how many nights it will take Niall to finish the book, we first need to determine how many pages he has left to read.
Total pages in the book: 520
Pages already read: 100
Pages left to read: 520 - 100 = 420
Niall plans to read 60 pages per night. To find out how many nights it will take him to read the remaining pages, we divide the pages left by the number of pages he reads per night:
420 pages left รท 60 pages per night = 7 nights
So, it will take him 7 nights to finish the book.