A bag contains 12 red marbles. If someone were to remove 2 marbles from the bag, one at a time, and replace the first marble after it was removed, the probability that neither marble would be red is 36/49. How many marbles are in the bag? Choose the correct choice from the following choices:
A) 24
B) 48
C) 84
D) 72
E) 80
ok let me see if i can explain what went on in the previous post   lets say i have x marbles in the bag in total --&gt; out of them 12 are red   so the probability of pulling a non-red marble is (x -12) / x   now the marble is placed back in the bag and we have x marbles again, of which again 12 are red. so the probability of pulling a non-red marble out is (x-12) / x   probability theorm states that if the probability of event A occuring is m and the probability of event B occuring is n then the probability of both A and B occuring is m*n   so therefore the probability of 2 non-red marbles getting pulled out is [(x-12)/x ] * [(x-12)/x]   this is given as 36/49   --&gt;(x-12)^2= 36/49   x^2   square rooting u have x-12/x = 6/7 or 7x-6x =84 or x =84   84
<result>C</result>
A bag contains 12 red marbles. If someone were to remove 2 marbles from the bag, one at a time, and replace the first marble after it was removed, the probability that neither marble would be red is 36/49. How many marbles are in the bag?