ANSWER: 95
Why?
83 is the average of 5 tests already taken. Each of the 5 tests would need 2 points added on in order to bring the average up to 85 (for those 5 tests). That means added 5 (tests) x 2 (extra points each) = 10 points to the 6th test to make up the difference.
10 + 85 = 95