This is incorrect! Call the two people "A" and "B". Suppose n= 1. The one thing can be given toeitherA or B. There are 2= 2^1, not 2^1- 2= -1, ways to "share". Suppose n= 2. We can give both things to A or give both things to B or give the first to A and the second to B or give the first to B and the second to A. There are 4= 2^2, not 2^2= 2, different ways. In general, there are 2^n, not 2^n- 2, ways to distribute n things among 2 people.

I don't know why they wrote "1+ 1" but that is simply 2^n because there are 2 people.And it used

(1+1)^n

But i dont get why they use (1+1)^n and im confused with the idea of 'sharing'.

Pretty much the same way. If there are 3 people, each thing can be given to any one of the 3: there are 3^n ways to do that.P.s: how do i solve if it's between 3 people?