Answer: Because A's wrong questions account for 1╱4 of the total, and both of them are wrong for 1╱6 of the total, so the total number of questions should be the common multiple of 4 and 6 (that is, the multiple of12:12,24,36 ...

Because B made three mistakes, and neither of them made more than three mistakes (1╱6 of the total), the total number of mistakes did not exceed 3/( 1╱6)= 18, so the total number of mistakes was 12.

Further calculation, A and B also did 9 right questions, 3 wrong questions and 2 wrong questions, so there were 8 right questions.