To find out how many more books need to have been checked out during March and April to reach a combined total of 750 books, we first need to calculate the total number of books checked out during those two months.
March: 6 book pictures * 50 books per picture = 300 books
April: 5 book pictures * 50 books per picture = 250 books
Total books checked out in March and April: 300 + 250 = 550 books
To reach a combined total of 750 books, we need 750 - 550 = 200 more books to have been checked out during March and April.
Therefore, 200 more books need to have been checked out during March and April to reach a combined total of 750 books.