In a group of 16 students, the probability of randomly selecting 2 girls in a row without replacing the names back is 1/12. How many girls are in the group?

This is a permutation (without replacement) so the probability is the probability of the first event times the probability of the second event. The equation would be ((x) / 16) * ((x-1) / (16-1)) = 1/12 don't ask me how I got this I'm not even sure myself. Algebra will give you an answer of x=5 or x=-4 and there can't be - 4 girls in the class so there must be 5 girls.