A group of 1280 individuals, consisting of teachers and students, is attending a conference. For every 15 students, there is one teacher. How many teachers are in the group ? 

Given :

A group of 1280 individuals, consisting of teachers and students, is attending a conference.

For every 15 students, there is one teacher.

Explanation :

Let the number of teachers be = t

Let the number of students be = s

According to the question for every 15 students, there is one teacher. This can be written as  :-

s = 15t 

Also, given the total number of individuals. Therefore,

s + t = 1280

Now, putting the value of s in the second equation :

15t + t = 1280

16t = 1280

t = 80

Now, substituting the value of t in the first equation :

s + 80 = 1280

s = 1200

Thus, number of the teachers in the group is 80.

Hence, "80" is the correct answer.