Two friends are taking an english class that has a monthly reading list. once a student chooses a book from the list, no other student can choose that book. if there are 3 mystery and 4 romance books left, what is the probability that the first friend will randomly select a mystery book and the second friend will randomly select a romance book?

Probability = Number of ways something can happen / Total number of outcomes; or:
P  = m / n
If the first friend randomly selects a mystery book the probability is:
3 / ( 3 + 4 ) = 3 / 7.
After that he leaves 2 mystery and 4 romance books. Probability that the second friend will randomly select a romance book is then :
4 / ( 2 + 4 ) = 4 / 6. And finally, the probability for all of that is:
P = 3 / 7 * 4 / 6 = 2 / 7.
The probability is 2 / 7.
 

The answer to your question would be b