以上 and 以下

The words 以上 and 以下 can be paired with something like a number + counter or a demonstrative pronoun (like これ) to mean "X or more" and "X or less", respectively. The sentences in Tobira demonstrated some other important grammar points that I liked, so I'm going to use those here.

健康のためには、毎日6時間以上寝るようにした方がいいそうだ。
For the sake of your health, I hear that you should make an effort to get 6 or more hours of sleep every day.

アメリカでは R 指定の映画は、18歳以上の人しか見られません。
In America, only people who are 18 years or older can see R-rated movies.

あまりお金がないので、プレゼントは50ドル以下の物にしようと思う。
Since I don't have much money, I think I'm going to do a gift that's less than $50.

コースを開くためには、学生が五人以上必要です。それ以下の場合は、キャンセルです。
In order for a course to open, there needs to be five or more students. If there are less than that, it's cancelled.