The average value over the interval is the area under the curve divided by the width of the interval.
Area = 4*(6 -1) +5(8 -6) = 30
Width = 8 - 1 = 7
Average value = 30/7 = 4 2/7
Area = 4*(6 -1) +5(8 -6) = 30
Width = 8 - 1 = 7
Average value = 30/7 = 4 2/7