What did the frontier mean to the nation in the first half of the nineteenth century?| pls help :)

Explanation:

in United States history, the advancing border that marked those lands that had been settled by Europeans. It is characterized by the westward movement of European settlers from their original settlements on the Atlantic coast (17th century) to the Far West (19th century).

answer; i do believe its (b) 12.5 years of age;

what is the tax base for the sales tax?

it should be (usually ) 6%