To write this equation in simplest form, we simply need to combine all like terms. The like terms in this particular expression are the terms with an n-variable and the terms with no variable. So we can combine them to simplify our expression.
5n - 6 + n - 1
First step, we can reorder our terms so that like terms are near each other
5n + n - 6 - 1
Now we can combine easily
(5n + n) - (6 - 1)
6n - 5
And that is your simplified expression.
5n - 6 + n - 1 in simplest form is 6n - 5.
Hope that helped! =)