You seem to have messed up everything here.. First of all, your questions tells you that 300 people were interviewed. Then what made you write that the people saw the advertisement in the newspaper and on Tv is 75/100???
also you seem to be unclear about union, intersection, and complement of sets..
(a) find the denominator you have written for (a) is wrong!!
(c) Do you know what complement of a set means? See the defintion in your book/notes