This is for algebra 2 and I got stuck on this anyone know this?

What signals you that factoring by grouping is the best method to use when factoring a problem?

Which expression can be used to determine the slope of the line that passes through the points -6, three and one, -9

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.