Answer:B) 

Explanation:
Step 1: list down the probability of the marbles,
 you will get the probability
 of 
 for the blue marbles and
 for the blue marbles and 
 for the red ones .
 for the red ones .
Step 2: Forget about the blue marbles and focus on the red marbles 
On the first pick of marbles the probability of getting a red marble is 
 but then you didn't replace the marble so now you have only 19 marbles as your total.
 but then you didn't replace the marble so now you have only 19 marbles as your total.
Step 3: lets say you picked a red marble on the first pick now you only have 7 red marbles out of 19 marbles (minus the red marble you picked -> step 2)
so the probability of getting a red marble on the second pick is 

Step 4: multiply the probabilities of both the first and second pick 
it will look like this 
 ×
 × 
 
 
 ^ ^
first pick second pick 
Note : You will only minus your probability and number of "marbles "( in this case ) if the question says "without replacing " 
final answer : 
