Hey guys, I am trying to figure out these two problems, but I cann't really understand what my teacher is asking for. Could someone please help?

1.) Prove each of the following statments, assuming that any conditioning event has positive probability. ( u denotes union, and n denotes intersection)

C) If A and B are mutually exclusive, then

P(A|AuB) = (P(A))/(P(A) + P(B))

D) P(AnBnC) = P(A|BnC)P(B|C)P(C)