Apublic library wants to place 4 magazines and 9 books on each display shelf. the expression 4s+9s represents the total number of items that will be displayed on s shelves. simplify the expression
!! 10 ! a westbound jet leaves central airport traveling 635 miles per hour. at the same time, an eastbound plane departs at 325 miles per hour. in how many hours will the planes be 1900 miles apart?