On the first day, the library helped 4 students, so 4 students x 5 books per student = 20 books were used.
On the second day, the library helped 5 students, so 5 students x 5 books per student = 25 books were used.
On the third day, the library helped 6 students, so 6 students x 5 books per student = 30 books were used.
In total, over the first three days, the library used 20 + 25 + 30 = 75 books.
The library initially had 120 books, so 120 - 75 = 45 books are remaining.
Each student needs 5 books, so the library can help 45 books / 5 books per student = 9 students on the fourth day.
#### 9
The answer is: 9
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
If the school library initially had 120 books and each student needs 5 books for their classes, the library was able to assist 4 students on the first day, 5 students on the second day, and 6 students on the third day. How many students can the library help on the fourth day of school?

### Answer:
