Help me due today it is math

What is the average rate of change for this function for the interval from x=2 to x=4 ?

At your job you're paid $50 per week plus $3 per sale at least how many saled do you need to make in order to have over $250

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)