Initial total number of marbles: 8 + 5 + 2 = 15
Initial number of blue marbles: 8
First pick:
p(blue marble) = 8/15
Since the marble from the first pick is returned to the bag, the bag still contains 8 blue marbles and a total of 15 marbles.
Second pick:
p(blue marble) = 8/15
Overall:
p(blue marble followed by blue marble) =
= p(blue marble) * p(blue marble)
= 8/15 * 8/15
= 64/225