Final answer:
Mr. Kent divided 312 books by 4 shelves to get 78 books on each shelf. He regrouped 0 tens as ones.
Step-by-step explanation:
To find the number of books on each shelf, Mr. Kent divided the total number of books (312) by the number of shelves (4). This gives us 78 books per shelf.
To find how many tens Mr. Kent regrouped as ones, we need to look at the division process. When 312 is divided by 4, there is no remainder. This means that there are no tens regrouped as ones.
Therefore, Mr. Kent regrouped 0 tens as ones. And there are 78 books on each shelf.