{Total} = {First correctly} + {Second correctly} - {Both correctly} + {Neither correctly}
100 = 85 + 65 - {Both correctly} + 5
{Both correctly} = 55.
This justifies what answer for what question? Q & A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
If 85 percent of the test takers taking an old paper and pencil GMAT exam answered the first question on a given math section correctly, and 65 percent of the test takers answered the second question correctly, and 5 percent of the test takers answered neither question correctly, what percent answered both correctly?
Options:
(A) 60 %
(B) 55 %
(C) 70%
(D) 75%
(E) 80%
(B)