Answer: The different ways can he line the textbooks up on his bookshelf =24
Explanation:
The number of ways to arrange n things = n!
Given: Number of different books = 4
Number of different ways to arrange 4 different books =4!
Number of different ways to arrange 4 different books= 4 x 3 x 2 x1
Number of different ways to arrange 4 different books = 24
Hence, the different ways can he line the textbooks up on his bookshelf =24