This problem is about a simple algebraic expression which we need to reduce in its simplest form. To do that, we need to reduce like terms, that is, terms that are similar, for example, terms 5x and 9x are similar because they have the same variable; also terms 12, 4, and 16 are also similar because they are single numbers.
Now, we reduce them using the algebraic sum properties, that is, numbers with the same sign will sum, and numbers with different signs will subtract:-
Then, we have
Therefore, the simplest expression is -4x-8.