What is -3xy equivalent to?

You put the following items into your rucksack. ham 600 g cheese 380 g tomatoes 270 g how much do all the ingredients weigh in total?

Standard deviation of 19,29,21,22,23

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