Hello,

part ii) will be the expected value, defined this way :

Here, the possible values for X are 3, 2 or -1 (if she finds the correct answer on her own, or thanks to her friend, or mistake).

So

P(X=3) : probability that she's right

P(X=2) : probability that she got wrong, then that her friend got right

P(X=-1) : probability that she's wrong and that her friend too