What is the result when the number 20 is decreased by 75%?

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?

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters

Will give brainliest for correct answer 8. use the distance time graph to answer these questions: a. what does the graph tell us about the velocity of the car? b. what is the average velocity of the car? (show work) c. is the velocity reflected in the graph positive or negative?d. is there any point on the graph where the car is not moving? how do we know?