What is the average amount paid in 2005

Asimple random sample of size nequals14 is drawn from a population that is normally distributed. the sample mean is found to be x overbar equals 70 and the sample standard deviation is found to be sequals13. construct a 90% confidence interval about the population mean

Add the two expressions 3.8b - 7 and 2.9b + 9 enter your answer in simplified form

When y’all answer can y’all explain too !