How to do 36-46? I don’t understand this at all

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

The weights of players in a basketball league are distributed normally. the distance (d) of each player's weight (w) from the mean of 86 kilograms was computed as follows: d = |w - 86| if d is greater than 7 for approximately 5% of the players, what is the approximate standard deviation of the players' weights? a. 1.75 kilograms b. 3.5 kilograms c. 4.3 kilograms d. 7 kilograms

Which of the following best describes the figure?