Which statement shows the associative property of addition? 7⋅(4⋅x)=(7⋅4)⋅x

13 + 5a = 5a + 13

(d + 4) + 17 = 17 + (d + 4)

(18 + 6) + y = 18 + (6 + y)

Suppose that 3% of all athletes are using the endurance-enhancing hormone epo (you should be able to simply compute the percentage of all athletes that are not using epo). for our purposes, a “positive” test result is one that indicates presence of epo in an athlete’s bloodstream. the probability of a positive result, given the presence of epo is .99. the probability of a negative result, when epo is not present, is .90. what is the probability that a randomly selected athlete tests positive for epo? 0.0297