Combine the like terms to make a simpler expression:
-n + (-3) + 3n +5

Like terms are terms that have the same variable. In this equation, your like terms are terms with n and terms without n. Put the like terms next to each other in the expression.

-n + 3n + (-3) + 5

Now, combine -n and 3n the same way you would combine -1 and 3.

2n + (-3) + 5

Next, combine -3 and 5.

2n + 2

Since 2n and 2 aren't like terms, your final answer will be 2n + 2.