There are four shelves of books along a wall in the library. on the top shelf, 16 of the 126 books are checked out. on the second shelf, 8 of the 137 books are checked out. on the bottom shelf, 17 of the 138 books are checked out. how many books are currently on the four shelves?

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z