### Instruction: Simplify the following expression:

$$5x + 6 - x + 12$$.### Response: So we have $5x+6-x+12$.
The first thing we can do is combine like terms.
So $5x + 6 - x + 12$ is the same as $4x + 18$.
Right. And we can factor out a $2$ to get $2(2x+9)$.