What is 21/8 as a mixed number? Please Help Quickly

Solve the system of equations. y= 2x y= x^2 - 15

Ben is three times as old as samantha, who is two years older than half of michel's age. if michel is 12. how old is ben?

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.