(3/4 - 1/2) divided by 3

Amonument at a park is in the shape of a right square pyramid. a diagram of the pyramid and its net are shown. what is the surface area of the monument? enter the answer in the box. m²

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?

3x = 729 solve for x plz . it's urgent. will mark