Question 662445
<pre>
The list of 11 consists of

1.  x
2.  x+1
3.  x+2
4.  x+3
5.  x+4
6.  x+5
7.  x+6
8.  x+7
9.  x+8
10. x+9
11. x+10

So x is the the smallest and y = x+10 is the largest.

16x<sup>-2</sup> = y<sup>-2</sup>

Using the definition of negative exponents:

{{{16/x^2}}} = {{{1/y^2}}}

Cross-multiply

16y² = x²

Since y = x+10, substitute x+10 for y

16(x+10)² = x²

Solve that for x, then find y from y = x+10, 

Then it'll be easy to find (x+y)

If you have trouble, you may ask me in the thank-you note.

Edwin</pre>