The area of a circle is pie*radius squared. To get the radius you half the diameter. 14 divided by 2 is of course 7 so 7*7 is 49, there you have the whole area of your banana cream pie. Now you need to find an eighth of that pie so you divide the whole pie (49cm squared) into 8 pieces which is 6.125cm squared per slice of pie. You need to find what is left over so simply take away 6.125 from 49 which leaves you with 42.875cm sq of banana cream pie left.