What is the equation that describes this rule - 0,-1,-2,-3,-4...

The depreciation per unit for a company

100 points, hi, i’m not sure how to get the equation from the graph and table.

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