Yesterday, Rita went on a bike ride. Her average speed was 9 miles per hour. Today, she went on another ride, this time averaging 12 miles per hour. In the two days, she biked for a combined total time of 13 hours. Let be the number of hours she biked yesterday. Write an expression for the combined total number of miles she biked in the two days.

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)