What Is an Open Sentence in Math Terms?

What is an open sentence in math terms? I'm Bon Crowder and we're talking about open sentences and also closed sentences a little bit. So a sentence in math is kind of like a sentence in English. It has a subject and a verb. So the sentence, 8 + 14 is 72, that equals is like the is so that's our verb, 8 + 14 subject, verb is 72 is the predicate nominative maybe. So, this statement, this sentence is false right, 8 + 14 isn't 72, that's crazy talk. But the fact that it's false means it's a closed sentence. We know for sure whether it's true or false. Likewise, 3 + 4 is 7, the sentence is true. We know for sure. These are both closed sentences. This guy however, X - 7 = 4. I don't know if he's true or not. Now you can tell me well X is clearly 11, well if X is indeed 11, then that's a true statement but X is in disguise, I don't really know what he is, X could be 85. If X is 85, that's a false sentence. So because this is who knows, true or false, this is an open sentence. I'm Bon Crowder and that's what an open sentence in math is.