A bag contains 6 red marbles, 3 blue marbles, and 7 green marbles. If a marble is randomly selected from the bag, what is the probability that it is blue?
The total number of marbles in the bag is 6 + 3 + 7 = <<6+3+7=16>>16.
The probability of selecting a blue marble is 3/16. Answer: \boxed{\dfrac{3}{16}}.