r = 6 ; w = 6 ???
a)
P(wrw) = P(wwr) = P(rww) = 6/12 * 6/12 * 6/12 = 1/8
b)
P(wrw) = P(wwr) = P(rww) = 6/12 * 6/11 * 5/10 = 3/22
c)
o.Z. P(www) = 6/12 * 5/11 * 4/10 = 1/11 = 0.0909
m.Z. P(www) = 6/12 * 6/12 * 6/12 = 1/8 = 0.125
man sollte also mit Zurücklegen ziehen.