Please help me, I've been struggling on this college math

Question

A bag contains 1 gold marbles, 9 silver marbles, and 28 black marbles. Someone offers to play this game: You randomly select one marble from the bag. If it is gold, you win $4. If it is silver, you win $3. If it is black, you lose $1.

What is your expected value if you play this game?

Answer 1

Expected value E = 4·1/38 + 3·9/38 - 1·28/38 = $3/38

Answer 2

The expected value E[X] = Summation((xi)(p(xi))

xi: the values of x

p(xi): the probability that X will take the value of xi.

you randomly select one marble from the bag. the expected value may be calculated by:

$4 for gold multiplied (1/38total marbles) + $3 silver (9/38total) - $1 black (28/38total) = ...

You subtract for black because it is loss so you want to subtract that from your expected value determination