There are (5 C 1) = 5! / (5 - 1)! = 5 ways of drawing a red marble, and (11 C 1) = 11! / (11 - 1)! = 11 ways of drawing any marble, so that the probability of drawing a red marble is 5/11.
After putting back the first marble, the probability of drawing another red is again 5/11.
So the probability of drawing 2 red marbles with replacement is (5/11)² = 25/121.
