Answer:
8.7
Explanation:
Add up all the books
5 students have 6 books each
3 students have 8 books each and so on
5 * 6 = 30
8*3 =24
9*6 = 54
12*4 = 48
-------------
156 books
Divide by the number of students
156/18 =8.6666666
Round to the nearest tenth
8.7
The average ( or mean) number of books per student is 8.7 books