Set theory

Let S has $n$ members, its member denoted by $x_1, x_2,\dots,x_n$ , and $\sum_{i=1}^nx_i = y$ . You will get the following equation:

$(\frac{y+1}{n+1}+13) = \frac{y}{n} = (\frac{y+2001}{n+1}-27)$

We resolve to find $n$ , which gives $y+1+40(n+1) = y+2001$ or $n = 49$ , then we proceed to find $y$ , which gives $13.02 = \frac{y}{2450}$ . What we need to find is mean of S, or $\frac{y}{49}$ , which, when solved, gives $y = 13.02\times\frac{2450}{49} = 13.02\times50 = 651$