The Northside Rifle team has two markspersons, and Sally. Hits the bull's eye 90% of the time and Sally hits a bully's eye 95% of the time.
(a) What is the probability that either or Sally or both will hit the bull's eye if each take one shot?
(b) What is the probability that and Sally will both hit the bull's eye?

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(a) I keep getting .925, while the book answer is .995
(b) I keep getting .855, while the book answer is .885
Please help me figure out how to work the problem to get the correct answer.

I did (.9 + .95) / 2 = .925
I did .9 * .95 = .855

For the first one, look at the probability that they both miss, and then use that to work out the probability that at least one of them hits. Or you can look in your notes on how to calculate P(A \cup B). There should be a formula that gives the same answer as the way that I suggested.

For the second one, I think you're right and the book's wrong.