A 12'' diameter pizza and a 16'' diameter pizza are each cut into eight congruent slices. Jane ate three slices of the 12'' pizza. Mark ate three slices of the 16'' pizza. How many more square inches of pizza than Jane did Mark eat? Express your answer as a common fraction in terms of (pie or 3.14).

A circle of radius r (inches) has area $\pi r^2$. "Three slices out of eight" is 3/8 of the whole pizza so Mark ate $(3/8)\pi (8)^2$ square inches of pizza and Jane ate $(3/8)\pi (6)^2$.