Please explain I have an exam in a bit

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

There are 45 questions on your math exam. you answered 810 of them correctly. how many questions did you answer correctly?

Scott’s bank account showed a balance of $750 on sunday. during the next five days, he made one deposit of $140 and numerous withdrawals of $180 each. let x represent the number of withdrawals that scott made. write an inequality that can be used to find the maximum number of withdrawals that scott could have made and maintain a balance of at least $100. do not use a dollar sign ($) in your response.