Acellus weekly time card please help

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

Do some research and find a city that has experienced population growth. determine its population on january 1st of a certain year. write an exponential function to represent the city’s population, y, based on the number of years that pass, x after a period of exponential growth. describe the variables and numbers that you used in your equation.

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'