If 75 percent of a class answered the first question on a certain test correctly, 30 percent answered the second question on the test correctly, and 20 percent answered neither of the questions correctly, what percent answered both correctly? Select the correct option:
A) 25 %  B) ( 8 ) 20 %  C) 30 %  D) 50 %  E) 65 %

Rationale: "i did n ' t understand how to connect 20 percent with the whole equation . why 20 is out of the percentile diagram ( circles ) but inside of 100 ? 20 % appeared in the exam ; however did not answer question aquestion b correctly so they are out of the two circles , however as they have appeared in the exam , they have to be taken into consideration for calculation purpose i am doing it this way : suppose the total class size is 100 , then 20 percent of the class answered incorrectly and rest 80 percent answered correctly in question 1 or 2 or both . now , 100 - [ ( 75 - x ) + x + ( 30 - x ) ] = 20 . . . . . . . . . . values are in percent x = 20 - 100 + 105 x = 25 ans : a"
Answer: A