Random variables in mathematics. Urgent! ! ! ! !

***36 cases 2 or 3 *** were repeated 4 times in 24 cases p=20/36=5/9.

The success numbers of the four experiments are 1.234 respectively.

P(X= 1)=C4 selection 1x (5/9) (4/9) 3.

P(x=2)=C4 Choose 2x (5/9) 2 (4/9) 2.

P(X=3)=C4 Choose 3x (5/9) 3 (4/9).

P(x=4)=C4 Select 4 (5/9) 4.

Mathematical expectation e =1XP1+2xp2+3xp3+4xp4.

Variance d = (xi-ex) 2xpi cumulative x from 1 to 4 p, and also from 1 to 4.