Heyy, i really need with this question

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

Convert 2000 swiss francs to dutch guilders

Josh has a rewards card for a movie theater he receives 15 points for becoming a rewards card holder he earns 3.5 points for each visit to the movie theater he needs at least 55 points to earn a free movie ticket which inequality can josh use to determine x, the minimum number of visits he needs to earn his first free movie ticket.