You and a friend get a pizza you eat 1/3 of the pizza and your friend eats 2/5 of the pizza how much of the pizza is left

If the scale factor between two circles is 2x/5y what is the ratio of their areas?

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.

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.