The probability of getting a particular color of marble, is given by the quotient between the number of marbles of that color and the total number of marbles.
Here we have:
5 red marbles.
7 green marbles.
4 black marbles.
8 blue marbles.
So the total number is 5 + 7 + 4 + 8 = 24.
Then:
P(red) = 5/24
P(orange) = 0/24 = 0 (because there are 0 orange marbles).