carols bookshelf has 4 shelves with 6 books on each .her brother robert has 3 shelves with 7 boson each. they want to combine their books. if they put 9 books on each shelf , how many shelves do they need?
you have to figure out the number of books that carols has which is 24 (6*4) then do the same with Robert, his is 21 (7*3) then add them to get 45 (24+21) now divide by 9 and your answer is 5.
