Answer:
Step-by-step explanation:
We consider 4 math books as one unit, 3 chemistry books as one unit and 2 history books as one unit and 1 language book as another unit(He wants to arrange his books so that all books dealing with same subject are together on the shelf)
Number of different arrangements possible = number of arrangements of 4 objects = 4! = 4 * 3 * 2 * 1 = 24