A bag contains 36 marbles, some of which are red and the rest are black. The black and red marbles are either clear or opaque. When a marble is randomly selected from the bag, the probability that it is red is 1/4 that is is opaque is 7/9 and that it is red or opaque is 11/12. How many marbles are black?
- How many marbles are black and opaque?