You can use your web browser to look at
help pages
and in the search box in the upper right corner you can type [[ and then tap Enter on your keyboard and it will take you to the documentation for Part. This is usually abbreviated by [[ and ]].
So with a list {a,b,c,d} you can extract the third item with {a,b,c,d}[[3]]
This works when you have lists inside of lists.
If you look at just the result from NSolve you should see that it has {{one solution},{another solution}}
When I just did c=c/.NSolve[...] there was {} around the value assigned to c. I did not want that so I used [[1]] to extract the first item and thus get rid of the {}.
You might find it helpful to quickly read an introduction to Mathematica programming. There are lots of books and even some web pages that will show you some of this. That might make it easier for you to become more productive.