the following table shows the test scores and sleep averages of several students. hours of sleep (x) 7 7 7 6 8 8 9 5 6 7 7 9 8 8 10 8 test score (y) 90 75 70 70 85 95 90 60 65 80 70 85 85 100 95 90 (a) use graphing technology (ti calculator or desmos) to find the linear regression equation that models the data. let x equal the hours of sleep and y equal test score. explain the steps you use. (b) use the equation to determine the approximate test score of a student who sleeps an average of 7.5 hours a night. show your work