Randomly picking a blue marble first will have a probability of 10/16, as there as 10 blue marbles out of the total of 16 (blue + red). Since it is not replaced, the total number of marbles will decrease to 15. So the probability of picking a red marble as the second marble becomes 6/15. In order to find the probability of picking a blue marble AND a red marble, we will have to multiply the two probabilities. (10/16) x (6/15) results in the probability of 60/240. Simplify this and you will get 1/4 or 0.25 which will be your final answer.
