Iwasn't at school today so i don't know how to do it

What is the maximum total area that 450cm of string can enclose if it is used to form perimeters of two adjoining rectangles as shown?

Fabian harvests 10 pounds of tomatoes from his garden. he needs 225 pounds to make a batch of soup. if he sets aside 2.8 pounds of tomatoes to make spaghetti sauce, how many batches of soup can fabian make?

Bob is putting books on a shelf and takes a break after filling 18 1/2 inches on the book shelf. the book shelf is now 2/3 full. how long is the entire bookshelf?