A bookseller sold ‘a’ number of Geography textbooks at the rate of  ₹   x per book, ‘a + 2’ number of History textbooks at the rate of  `₹ (x + 2) per book and ‘a – 2‘ number of Mathematics textbooks at the rate of    ₹ (x – 2) per book. What is his total sale in   ₹ ?

The correct option is 3ax + 8.

To find the total sale of the bookseller, we need to calculate the sale amount for each subject's textbooks and then sum them up. The sale amount for any type of textbook is given by the product of the number of textbooks sold and the rate per book.

Let's calculate the sale amount for each subject step-by-step:

1. Geography textbooks:
Number of books sold = a
Rate per book = ₹ x
Sale from Geography textbooks = $a·x$ = $ax$

2. History textbooks:
Number of books sold = a + 2
Rate per book = ₹ (x + 2)
Sale from History textbooks = $(a+2)(x+2)$

Expanding this expression:
$(a+2)(x+2)=a(x+2)+2(x+2)=ax+2a+2x+4$

3. Mathematics textbooks:
Number of books sold = a - 2
Rate per book = ₹ (x - 2)
Sale from Mathematics textbooks = $(a-2)(x-2)$

Expanding this expression:
$(a-2)(x-2)=a(x-2)-2(x-2)=ax-2a-2x+4$

Now, we find the total sale by adding the three individual sales together:

Total Sale = (Sale from Geography) + (Sale from History) + (Sale from Mathematics)

Total Sale = $\left(ax\right)+(ax+2a+2x+4)+(ax-2a-2x+4)$

Grouping the like terms together:
Total Sale = $(ax+ax+ax)+(2a-2a)+(2x-2x)+(4+4)$

Simplifying each grouped term:
- The sum of the $ax$ terms is $3ax$.
- The $2a$ and $-2a$ terms cancel each other out ($0$).
- The $2x$ and $-2x$ terms cancel each other out ($0$).
- The constant terms add up to $4+4=8$.

Combining these simplified parts, we get:
Total Sale = $3ax+8$

Thus, the bookseller's total sale is ₹ (3ax + 8).