What is the sum of sqrt 18 plus sqrt 72

Use set builder notation to represent the following set: { -3, -2, -1, 0}

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

Can someone tell me if this is perpendicular? !