Question 848623
Make two outcomes:  Red, Not Red.

We have 105 marbles and 18 of them are red.

So we define a binomial distribution where 

p[red] = 18/(30+18+26+31) = 6/35

The expected value of a binomial with n trials and p = probability of success is  n*p.

We take 8* (6/35)=  48/35  = 1.37

Since we cannot draw 1.37 red marbles. We say we expect 1 marble to be red.