P=[C(2，3)/C(2，5)]*[C( 1， 1)C( 1，2)/C(2，3)]

(2) There are several ways to win the prize: 1, touch the two white balls in box A; 2. Touch a white ball in box A and a white ball in box B. Therefore, p = c (2 2,3)/c (2,5)+[c (1,3) c (1, 2)] * [c (1.

(3) Ten

1

2

P

e(X)= 0+ 1 * P(X = 1)+2 * P(X = 2)

Add: If you don't understand anything, you can continue to ask. The following are three probabilities of the problem (3).

Get the winning probability from (2) (I didn't count it, let's set it as P)

P(X=0)=( 1-p)( 1-p)

P(X = 1)= 1-P(X = 0)-P(X = 2)

P(X=2)=p*p