Need help with the reasons

This week, conrad will work 1 3/4 times longer than last week. giovanni will work 1 1/3 times longer than last week. sally will work 2/3 the number of hours she worked last week. match each employee's name to the number of hours he or she will work this week

Determine whether the set of whole numbers is closed under addition. explain why the set is or is not closed. give an example.

Use set buikder notation to represent the following set: {, -2, -1, 0}