Find the sum. Express your answer in simplest form. 9a^2-5/b^2+2 + -2a^2+4/b^2+2

Asurvey of 45 teens found that they spent an average of 25.6 hours per week in front of a screen (television, computer, tablet, phone, based on the survey’s sample mean, which value could be the population mean? 2.3 hours 27.4 hours 75.3 hours 41.5 hours