请求帮忙!

1，A target shooter participates in 2 tournaments.She has a 20 percent chance of winning the first tournament and a 30 percent chance of winning the second tournament.What is the probability that she will win exactly one of them?

the answer is 38%, I am just wondering how can make it?

2,A fair coin is tossed 5 times.what is the probability that it lands heads up at lease twice?       

 is the answer 13/16? 

3,A canoeist paddled upstream at 10 meters per minute, turned around, and drifted downstream at 15 meters.If the distance traveld in each direction was the same,and the time spend turning the canoe around was negligible, what was the canoeist's average speed over the course of the journey, in meters per minute? 

No ideas about this Q.

1. 20%*70%+80%*30%=38%

2.1-[(1/2)^5+C(5,1)*(1/2)^5]=13/16

3. S for distance

2S/[(S/10)+(S/15)]=12