If 63 percent of a class answered the first question on a certain test correctly, 50 percent answered the second question on the test correctly, and 20 percent answered neither of the questions correctly, what percent answered both correctly?
Choose one:
A) 24 %	B) 27 %	C) 30 %	D) 33 %	E) 36 %

Rationale: "63 % answered the first question correctly and 20 % answered neither correctly . then 17 % missed the first question but answered the second question correctly . then the percent who answered both correctly is 50 % - 17 % = 33 % . the answer is d ."
Answer: D