Because the number of books on the last three shelves is equal, the books on the three shelves are all 450/3= 150 (books), and C takes out 30 books and puts them in A. That is to say, before C takes out 30 books, A has 150-30= 120 (books) on the shelf.

1 m2 = 100 square decimeter 10 times 10 equals 100, so the answer is 10. I wish you progress in your study.

44×3= 132 77×3=23 1