Hi Justin,
I drew a graph of the function f(x) from x = 0 to x = 7 and shaded orange the region between the the graph of f(x), the xaxis and the lines x = 0 and x = 7. The average of the function over this interval is the height h so that the area of the region shaded orange is the same as the area of the rectangle OPQR.
The area of the rectangle is 7 h and the area of the rectangle you can find using geometry or calculus.
Penny
