Answer:
2, 4, 6 are expressions
Explanation:
A math sentence has a verb: "is equal to" It could also be some other, similar phrase, such as "is less than" or "is not equal to," for example.
An expression has no verb!
x - 6 Say it out loud. See? No verb. It's like saying "that evil neighbor of mine" without saying anything more. Yes? Did what? Is what? Compares to what?