Final answer:
The expression 2n + - n - 4 simplifies to n - 4 by combining like terms: 2n and -n add up to n, with the constant -4 remaining unchanged.
Step-by-step explanation:
The question involves a straightforward algebraic simplification. The variable, n, stands for a number that a spectator chooses. Computing the expression 2n + - n - 4, we must combine like terms, which are the terms containing n. Adding 2n and -n together gives us n, and since there are no other terms with n, the expression simplifies to n - 4.
To generalize, in this type of problem, we perform the arithmetic operations in the usual order, taking care of addition and subtraction of variables and constants separately. The result is a simplified expression in terms of the same variable that was chosen by the spectator.