Answer:
There are 60 books in total.
Explanation:
There is a set of books with 3x8. So three groups of eight books. So all you have to do is multiply 3x8 or 8x3. Or you could even add 8 three times, 8+8+8. Both ways would lead you to the product/sum of 24.
Then you would do the same with the second set of books. 4x9. So four groups of nine books. You would then multiply 4x9 or 9x4. Or even add 9 four times, 9+9+9+9. Both ways would lead you to the product/sum of 36.
For the final step to see how many books there are in all, you would just have to add the two products/sums. 24+36 = 60