Solution
Step 1
Write out an expression for the probability

Step 2
Define terms
Total number of events = 8 marbles
Number of required events = red then marble
Number of red = 2 marbles2
Number of green = 2 marbles
Note: The question is without replacement.
Step 3
Get the required probabilities and the answer

Hence the Pr(of red then green) is given as

Hence the probability of picking a red marble then a green marble = 1/14