Jake and mike took a different number of tests. jake scored 85 points on each test. mike's total score was 15 less than jake's total score. the following expression shows mike's total score:

85x − 15

in the expression, what does the variable x represent?
the total number of tests mike took
the total number of tests jake took
the sum of jake's and mike's total score
the difference between jake's and mike's total score

An automobile assembly line operation has a scheduled mean completion time, μ, of 12 minutes. the standard deviation of completion times is 1.6 minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of 33 completion times under new management was taken. the sample had a mean of 11.2 minutes. assume that the population is normally distributed. can we support, at the 0.05 level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed.