Final answer:
The probability of drawing a blue marble is 0.6 or 60%.
Step-by-step explanation:
The probability of drawing a blue marble can be found by dividing the number of blue marbles in the bag by the total number of marbles in the bag. In this case, there are 12 blue marbles out of a total of 20 marbles. So the probability of drawing a blue marble is 12/20 = 0.6.
This can also be expressed as a percentage by multiplying the probability by 100. So the probability of drawing a blue marble is 0.6 * 100 = 60%.