Meghan sells advertisements for a radio station. Each 30 second ad costs $20 per play, and each 60 second ad costs $35 per play. Meghan sold 12 ads for $315. She wrote the system below letting x represent the number of 30 second ads and y represent the number of 60 second ads. X y = 12. 20 x 35 y = 315. What is the solution to the system of equations? (3, 9) (6, 6) (7, 5) (11, 1).

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)