We already worked out the probabilities before:

Possible Outcome RR RB BR BB
xi `2` `1` `1` `0`
P(xi) `2/15` `4/15` `4/15` `1/3`

`E(X)=sum{x_i * P(x_i)}`

`=2times2/15+` `1times4/15+` `1times4/15+` `0times1/3`

`=4/5`

`=0.8`

This means that if we performed this experiment 1000 times, we would expect to get 800 red balls.