Hey Nadeshiko.
Hint: If you eat n pieces of pizza then you eating n/8*pi*r^2 in terms of square lengths of the pizza (inches for your example). Try expressing your answer as a ratio of the different pieces of pizza.
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).
Please tell me how you got the answer! Thanks.