Right, so I've got an upcoming exam tomorrow, and I just found out I'm stuck on probabilities (Not sure if that is what it's called in English).

Anyways, the question goes like this :

Troms skiing facility got 6 menn for NM in skiing. 2 of them are under the age of 20. It's a 4x7,5km lap, and they are going to pick 4 "runners(/skiiers)".

a) What's the probablity for that NONE of the 2 under the age of 20 does this?

b) What's the probablity for that minimum ONE of the 2 under the age of 20 does this?

c) What's the probablity for that EXACTLY ONE of the 2 under the age of 20 does this?

d)What's the probability that the skiier hit at least 4 of 5 targets with 5 shots.? (Hitting 1 target = 90%)

If you could explain your answers, that would be great.

I will most likely understand it, if you just set it up correctly.

(Not even sure if I've been trying the right formula :

X=x (n) p^x (1-p)^n-x

----(x) (<- not n divided by x)

OR if you could do :

Statistic over football matches in 2005 showed the probabilities for home victiory (H), tie (T), away victory (A).

P(H) = 0,45, P(U) = 0,29, P(B)= 0,26

a) What's the probability that ALL the twelve matches ends with home victory?

b) How big is the posibility that the 6 first ends with home victory, and the next tree tie, and the last tree with away victory?

c) Probability that there won't be an away victory?