The librarian’s assistant is given $200 to buy a collection of books for the library. paperback books cost $3.50 each, and hardcover books cost $8 each. the librarian wants at least 20 hardcover books for the collection. which of the following systems correctly describes the number of paperbacks (p) and hardcover books (h) the assistant can purchase

Anew test for ra is being developed. the test is administered to 750 patients with ra and 750 without ra. for the sake of the question, assume the prevalence of ra in this population is 50%. of the 750 patients with ra, 575 have a positive result. of the 750 patients without ra, 150 have a positive result. what is the positive predictive value of the new test? a575/(575+150) b. 600/(600+ 150) c. 575/(575+125) d. 600/(600+ 125)