Sorry, I did them out of order because I started doing the second problem first on accident.
For the second question: the probability that you choose a green marble is 2/(2 + 3 + 3) = 2/8 = 1/4. The probability that you choose a red marble without replacing the green one is: 3/(2 + 3 + 3 - 1) = 3/7. Now, multiply these two fractions together because they depend on each other:
1/4 * 3/7 = 3/28
For the first question: the probability you choose a green marble is still 1/4. The probability that you choose a yellow marble is 3/(2 + 3 + 3 - 1) = 3/7. Multiply these two fractions together and you get: 1/4 * 3/7 = 3/28 again.
