First to people get marked brainliest

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

The ratio of wooden bats to metal bats in the baseball coach’s bag is 2 to 1. if there are 20 wooden bats, how many metal bats are in the bag?

An arithmetic series a consists of consecutive integers that are multiples of 4 what is the sum of the first 9 terms of this sequence if the first term is 0