Let's use the letter M to label the math class. The fact that person y is in that class can be expressed by:
[tex]y\in M[/tex]We also have to show that is older than 100 so we have:
[tex]y>100[/tex]If we put all this information together we get:
[tex]\mleft\lbrace y\colon y\in M,y>100\mright\rbrace[/tex]And that's an alternative way to express the set.
