Find the perimeter of a regular decagon if the radius is 18. Round to the nearest tenth if necessary.

For one history test, keith had to answer 40 questions. of these 40 questions, keith answered 28 of them correctly. what percent did keith get on his history test? round your answer to the nearest tenth if necessary

Barbara deposited $300 in the bank. if the bank pays her simple interest at the rate of 4 percent per year, how much money will she have in her account at the end of 9 months?

We just started the introduction into circles and i have no idea how to do this.