Concept:Mean is the sum of all observations divided by the number of observations.Explanation:First, list the observations: 10,8,−9,−12,15,0,23,−3,−2,−13,−24,28,35,42.There are 14 observations.Calculate the sum: 10+8=18, 18−9=9, 9−12=−3, −3+15=12, 12+0=12, 12+23=35, 35−3=32, 32−2=30, 30−13=17, 17−24=−7, −7+28=21, 21+35=56, 56+42=98.Sum = 98.Mean = 1498​=7.Answer:7