Hi
Let number of friends be n
Now the question says there are 195 chocolates along with contribution of each friend that is equal to number of friends .
So if number of friends are n and so each friend will contribute n chocolates so total contribution will become n^2
Now therefore total chocolates will become : 195+n^2
Now it says when divided equally , the chocolates becomes 28
so we get (n^2+195)/n =28
n^2+195=28n
n^2-28n+195=0
(n-15)(n-13)=0
n=15 or 13.
So number of friends can be 13 or 15.