(x8^2 -15x)-(x^2-27x)=ax^2+bx if the equation above is true for all values of x, what is the value of b-a?

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